diff --git a/src/backend/access/aocs/aocsam.c b/src/backend/access/aocs/aocsam.c
index 870cfbe4b9e..267dd837697 100644
--- a/src/backend/access/aocs/aocsam.c
+++ b/src/backend/access/aocs/aocsam.c
@@ -1012,6 +1012,7 @@ aocs_insert_init(Relation rel, int segno)
 	desc = (AOCSInsertDesc) palloc0(sizeof(AOCSInsertDescData));
 	desc->aoi_rel = rel;
 	desc->appendOnlyMetaDataSnapshot = RegisterSnapshot(GetCatalogSnapshot(InvalidOid));
+	desc->insertMultiFiles = false;
 
 	/*
 	 * Writers uses this since they have exclusive access to the lock acquired
@@ -1072,10 +1073,9 @@ aocs_insert_init(Relation rel, int segno)
 											(FileSegInfo *) desc->fsInfo, desc->lastSequence,
 											rel, segno, tupleDesc->natts, true);
 
-	/* should not enable insertMultiFiles if the table is created by own transaction */
-	desc->insertMultiFiles = enable_parallel &&
-							gp_appendonly_insert_files > 1 &&
-							!ShouldUseReservedSegno(rel, CHOOSE_MODE_WRITE);
+	/* Should not enable insertMultiFiles if the table is created by own transaction or in utility mode */
+	if (Gp_role != GP_ROLE_UTILITY)
+		desc->insertMultiFiles = gp_appendonly_insert_files > 1 && !ShouldUseReservedSegno(rel, CHOOSE_MODE_WRITE);
 	return desc;
 }
 
diff --git a/src/backend/access/appendonly/appendonlyam.c b/src/backend/access/appendonly/appendonlyam.c
index b5993e30f4f..4d84e957026 100755
--- a/src/backend/access/appendonly/appendonlyam.c
+++ b/src/backend/access/appendonly/appendonlyam.c
@@ -2664,6 +2664,7 @@ appendonly_insert_init(Relation rel, int segno)
 
 	aoInsertDesc->aoi_rel = rel;
 	aoInsertDesc->range = 0;
+	aoInsertDesc->insertMultiFiles = false;
 
 	/*
 	 * We want to see an up-to-date view of the metadata. The target segment's
@@ -2851,10 +2852,9 @@ aoInsertDesc->appendOnlyMetaDataSnapshot, //CONCERN:Safe to assume all block dir
 											aoInsertDesc->fsInfo, aoInsertDesc->lastSequence,
 											rel, segno, 1, false);
 
-	/* should not enable insertMultiFiles if the table is created by own transaction */
-	aoInsertDesc->insertMultiFiles = enable_parallel &&
-									gp_appendonly_insert_files > 1 &&
-									!ShouldUseReservedSegno(rel, CHOOSE_MODE_WRITE);
+	/* Should not enable insertMultiFiles if the table is created by own transaction or in utility mode */
+	if (Gp_role != GP_ROLE_UTILITY)
+		aoInsertDesc->insertMultiFiles = gp_appendonly_insert_files > 1 && !ShouldUseReservedSegno(rel, CHOOSE_MODE_WRITE);
 	return aoInsertDesc;
 }
 
diff --git a/src/backend/utils/misc/guc_gp.c b/src/backend/utils/misc/guc_gp.c
index 53cb6e9d6a8..2e39cea261c 100644
--- a/src/backend/utils/misc/guc_gp.c
+++ b/src/backend/utils/misc/guc_gp.c
@@ -3177,7 +3177,7 @@ struct config_int ConfigureNamesInt_gp[] =
 			NULL
 		},
 		&gp_appendonly_insert_files,
-		4, 0, 127,
+		4 /* CBDB_PARALLEL If default value is changed, set it in src/test/regress/GNUMakefile too, see details there */, 0, 127,
 		NULL, NULL, NULL
 	},
 
diff --git a/src/test/isolation2/Makefile b/src/test/isolation2/Makefile
index 0fed5742cd6..aec939457e7 100644
--- a/src/test/isolation2/Makefile
+++ b/src/test/isolation2/Makefile
@@ -63,7 +63,11 @@ clean distclean:
 install: all gpdiff.pl gpstringsubs.pl
 
 installcheck: install installcheck-parallel-retrieve-cursor
-	$(pg_isolation2_regress_installcheck) --init-file=$(top_builddir)/src/test/regress/init_file --init-file=./init_file_isolation2 --schedule=$(srcdir)/isolation2_schedule
+	(\
+	gpconfig -c gp_appendonly_insert_files -v 0; \
+	gpstop -u; \
+	$(pg_isolation2_regress_installcheck) --init-file=$(top_builddir)/src/test/regress/init_file --init-file=./init_file_isolation2 --schedule=$(srcdir)/isolation2_schedule \
+	)
 
 installcheck-resgroup: install
 	$(pg_isolation2_regress_installcheck) --init-file=$(top_builddir)/src/test/regress/init_file --init-file=./init_file_resgroup --dbname=isolation2resgrouptest --schedule=$(srcdir)/isolation2_resgroup_schedule
@@ -74,6 +78,8 @@ installcheck-parallel-retrieve-cursor: install
 # Add a new rule for running installcheck with parallel mode enabled.
 installcheck-cbdb-parallel: install
 	(\
-	export PGOPTIONS='-c optimizer=off -c enable_parallel=true  -c gp_appendonly_insert_files=0'; \
+	gpconfig -c gp_appendonly_insert_files -v 0; \
+	gpstop -u; \
+	export PGOPTIONS='-c optimizer=off -c enable_parallel=true'; \
 	$(pg_isolation2_regress_installcheck) --init-file=$(top_builddir)/src/test/regress/init_file --init-file=./init_file_isolation2 --schedule=$(srcdir)/isolation2_schedule \
 	)
\ No newline at end of file
diff --git a/src/test/regress/GNUmakefile b/src/test/regress/GNUmakefile
index 70dddce82aa..d16d70385a5 100644
--- a/src/test/regress/GNUmakefile
+++ b/src/test/regress/GNUmakefile
@@ -204,8 +204,18 @@ installcheck: installcheck-good
 installcheck-small: all
 	$(pg_regress_installcheck) $(REGRESS_OPTS) --schedule=$(srcdir)/parallel_schedule $(EXTRA_TESTS)
 
+# We have set default gp_appendonly_insert_files = 4 for user's underlying parallelism.
+# But that will cause lots of diffs between non-parallel and parallel mode that we can't
+# afford to modify them one by one, or create lots of answer files(and we didn't support that yet).
+# Any tests related to ao parallel should set GUCs in their own sql files, like gp_parallel.
+# Using gpconfig is a workaround for regression test for non-parallel and parallel mode.
+# Same for src/test/isolation2/Makefile
 installcheck-good: all twophase_pqexecparams hooktest query_info_hook_test
-	$(pg_regress_installcheck) $(REGRESS_OPTS) --schedule=$(srcdir)/parallel_schedule --schedule=$(srcdir)/greenplum_schedule $(EXTRA_TESTS)
+	(\
+	gpconfig -c gp_appendonly_insert_files -v 0; \
+	gpstop -u; \
+	$(pg_regress_installcheck) $(REGRESS_OPTS) --schedule=$(srcdir)/parallel_schedule --schedule=$(srcdir)/greenplum_schedule $(EXTRA_TESTS) \
+	)
 
 installcheck-parallel: all
 	$(pg_regress_installcheck) $(REGRESS_OPTS) --schedule=$(srcdir)/parallel_schedule $(MAXCONNOPT) $(EXTRA_TESTS)
diff --git a/src/test/regress/expected/gp_parallel.out b/src/test/regress/expected/gp_parallel.out
index 306c1119bb3..04e8184f622 100644
--- a/src/test/regress/expected/gp_parallel.out
+++ b/src/test/regress/expected/gp_parallel.out
@@ -35,6 +35,8 @@ set force_parallel_mode = 0;
 set optimizer = off;
 create schema test_parallel;
 set search_path to test_parallel;
+-- set this to default in case regress change it by gpstop.
+set gp_appendonly_insert_files = 4;
 create table ao1(x int, y int) with(appendonly=true);
 NOTICE:  Table doesn't have 'DISTRIBUTED BY' clause -- Using column named 'x' as the Greenplum Database data distribution key for this table.
 HINT:  The 'DISTRIBUTED BY' clause determines the distribution of data. Make sure column(s) chosen are the optimal data distribution key to minimize skew.
@@ -48,7 +50,8 @@ begin;
 -- encourage use of parallel plans
 set local min_parallel_table_scan_size = 0;
 set local max_parallel_workers_per_gather = 4;
-set local enable_parallel = true;
+-- test insert into multiple files even enable_parallel is off.
+set local enable_parallel = off;
 -- insert multiple segfiles for parallel
 set local gp_appendonly_insert_files = 4;
 -- test appendonly table parallel 
@@ -62,6 +65,7 @@ select segfilecount from pg_appendonly where relid = 'ao1'::regclass;
             4
 (1 row)
 
+set local enable_parallel = on;
 explain(costs off) select count(*) from ao1;
                     QUERY PLAN                    
 --------------------------------------------------
@@ -79,6 +83,7 @@ select count(*) from ao1;
 (1 row)
 
 -- test aocs table parallel 
+set local enable_parallel = off;
 insert into aocs1 select i, i from generate_series(1, 1200000) g(i);
 analyze aocs1;
 select segfilecount from pg_appendonly where relid = 'aocs1'::regclass;
@@ -87,6 +92,7 @@ select segfilecount from pg_appendonly where relid = 'aocs1'::regclass;
             4
 (1 row)
 
+set local enable_parallel = on;
 explain(costs off) select count(*) from aocs1;
                     QUERY PLAN                    
 --------------------------------------------------
@@ -1698,5 +1704,6 @@ abort;
 -- start_ignore
 drop schema test_parallel cascade;
 -- end_ignore
+reset gp_appendonly_insert_files;
 reset force_parallel_mode;
 reset optimizer;
diff --git a/src/test/regress/sql/gp_parallel.sql b/src/test/regress/sql/gp_parallel.sql
index 6b68b31ebae..e52226a68b9 100644
--- a/src/test/regress/sql/gp_parallel.sql
+++ b/src/test/regress/sql/gp_parallel.sql
@@ -36,6 +36,8 @@ set optimizer = off;
 
 create schema test_parallel;
 set search_path to test_parallel;
+-- set this to default in case regress change it by gpstop.
+set gp_appendonly_insert_files = 4;
 
 create table ao1(x int, y int) with(appendonly=true);
 create table ao2(x int, y int) with(appendonly=true);
@@ -46,7 +48,8 @@ begin;
 -- encourage use of parallel plans
 set local min_parallel_table_scan_size = 0;
 set local max_parallel_workers_per_gather = 4;
-set local enable_parallel = true;
+-- test insert into multiple files even enable_parallel is off.
+set local enable_parallel = off;
 
 -- insert multiple segfiles for parallel
 set local gp_appendonly_insert_files = 4;
@@ -57,13 +60,16 @@ analyze ao1;
 insert into ao2 select i%10, i from generate_series(1, 1200000) g(i);
 analyze ao2;
 select segfilecount from pg_appendonly where relid = 'ao1'::regclass;
+set local enable_parallel = on;
 explain(costs off) select count(*) from ao1;
 select count(*) from ao1;
 
 -- test aocs table parallel 
+set local enable_parallel = off;
 insert into aocs1 select i, i from generate_series(1, 1200000) g(i);
 analyze aocs1;
 select segfilecount from pg_appendonly where relid = 'aocs1'::regclass;
+set local enable_parallel = on;
 explain(costs off) select count(*) from aocs1;
 select count(*) from aocs1;
 
@@ -508,5 +514,6 @@ abort;
 drop schema test_parallel cascade;
 -- end_ignore
 
+reset gp_appendonly_insert_files;
 reset force_parallel_mode;
 reset optimizer;