diff --git a/src/pl/plpython/expected/plpython3_path_guc.out b/src/pl/plpython/expected/plpython3_path_guc.out
new file mode 100644
index 000000000000..36800df553f9
--- /dev/null
+++ b/src/pl/plpython/expected/plpython3_path_guc.out
@@ -0,0 +1,39 @@
+--
+-- Tests for functions that return set PYTHONPATH guc only for gpdb6 plpython3
+--
+LOAD 'plpython3';
+show plpython3.python_path;
+ plpython3.python_path 
+-----------------------
+ 
+(1 row)
+
+set plpython3.python_path='/foo';
+show plpython3.python_path;
+ plpython3.python_path 
+-----------------------
+ /foo
+(1 row)
+
+-- Set up test path functions first.
+CREATE FUNCTION test_path_added() 
+RETURNS text AS $$
+  import sys
+  return str(sys.path[0])
+$$ language plpython3u;
+SELECT test_path_added();
+ test_path_added 
+-----------------
+ /foo
+(1 row)
+
+-- when the plpython init can not set again --
+set plpython3.python_path='/bar';
+ERROR:  SET PYTHONPATH failed, the GUC value can only be changed before initializing the python interpreter.
+-- run again the path will not change still /foo --
+SELECT test_path_added();
+ test_path_added 
+-----------------
+ /foo
+(1 row)
+
diff --git a/src/pl/plpython/plpy_main.c b/src/pl/plpython/plpy_main.c
index e29fb744d314..4425d593d57a 100644
--- a/src/pl/plpython/plpy_main.c
+++ b/src/pl/plpython/plpy_main.c
@@ -17,6 +17,8 @@
 #include "utils/rel.h"
 #include "utils/syscache.h"
 
+#include "cdb/cdbvars.h"
+
 #include "plpython.h"
 
 #include "plpy_main.h"
@@ -81,6 +83,23 @@ void PLy_handle_cancel_interrupt(void);
 
 bool PLy_enter_python_intepreter = false;
 
+static bool inited = false;
+
+/* GUC variables */
+#if PY_MAJOR_VERSION >= 3
+static char *plpython3_path = NULL;
+
+static bool 
+plpython3_check_python_path(char **newval, void **extra, GucSource source) {
+	if (inited)
+	{
+		GUC_check_errmsg("SET PYTHONPATH failed, the GUC value can only be changed before initializing the python interpreter.");
+		return false;
+	}
+	return true;
+}
+#endif
+
 void
 _PG_init(void)
 {
@@ -137,6 +156,18 @@ _PG_init(void)
 	prev_cancel_pending_hook = cancel_pending_hook;
 	cancel_pending_hook = PLy_handle_cancel_interrupt;
 
+#if PY_MAJOR_VERSION >= 3
+	DefineCustomStringVariable("plpython3.python_path",
+							gettext_noop("PYTHONPATH for plpython3."),
+							NULL,
+							&plpython3_path,
+							"", // default path need to set empty for init
+							PGC_USERSET, 
+							GUC_GPDB_NEED_SYNC,
+							plpython3_check_python_path,
+							NULL, 
+							NULL);
+#endif
 	pg_bindtextdomain(TEXTDOMAIN);
 }
 
@@ -148,7 +179,6 @@ _PG_init(void)
 static void
 PLy_initialize(void)
 {
-	static bool inited = false;
 
 	/*
 	 * Check for multiple Python libraries before actively doing anything with
@@ -162,18 +192,23 @@ PLy_initialize(void)
 		ereport(FATAL,
 				(errmsg("multiple Python libraries are present in session"),
 				 errdetail("Only one Python major version can be used in one session.")));
-
+#if PY_MAJOR_VERSION >= 3
+	/* PYTHONPATH and PYTHONHOME has been set to GPDB's python2.7 in Postmaster when
+	 * gpstart. So for plpython3u, we need to unset PYTHONPATH and PYTHONHOME.
+	 * if user set PYTHONPATH then we set it in the env
+	 */
+	if (plpython3_path && *plpython3_path) 
+		setenv("PYTHONPATH", plpython3_path, 1);
+	else 
+		unsetenv("PYTHONPATH");
+		unsetenv("PYTHONHOME");
+#endif
 	/* The rest should only be done once per session */
 	if (inited)
 		return;
 
 #if PY_MAJOR_VERSION >= 3
 	PyImport_AppendInittab("plpy", PyInit_plpy);
-	/* PYTHONPATH and PYTHONHOME has been set to GPDB's python2.7 in Postmaster when
-	 * gpstart. So for plpython3u, we need to unset PYTHONPATH and PYTHONHOME.
-	 */
-	unsetenv("PYTHONPATH");
-	unsetenv("PYTHONHOME");
 #endif
 	Py_Initialize();
 #if PY_MAJOR_VERSION >= 3
diff --git a/src/pl/plpython/sql/plpython3_path_guc.sql b/src/pl/plpython/sql/plpython3_path_guc.sql
new file mode 100644
index 000000000000..e686e7670771
--- /dev/null
+++ b/src/pl/plpython/sql/plpython3_path_guc.sql
@@ -0,0 +1,23 @@
+--
+-- Tests for functions that return set PYTHONPATH guc only for gpdb6 plpython3
+--
+LOAD 'plpython3';
+show plpython3.python_path;
+
+set plpython3.python_path='/foo';
+show plpython3.python_path;
+
+-- Set up test path functions first.
+CREATE FUNCTION test_path_added() 
+RETURNS text AS $$
+  import sys
+  return str(sys.path[0])
+$$ language plpython3u;
+
+SELECT test_path_added();
+
+-- when the plpython init can not set again --
+set plpython3.python_path='/bar';
+
+-- run again the path will not change still /foo --
+SELECT test_path_added();
diff --git a/src/pl/plpython3/Makefile b/src/pl/plpython3/Makefile
index 3752adfa1245..2769e32c19f5 100644
--- a/src/pl/plpython3/Makefile
+++ b/src/pl/plpython3/Makefile
@@ -92,6 +92,7 @@ REGRESS = \
 	plpython_schema \
 	plpython_populate \
 	plpython_test \
+	plpython3_path_guc \
 	plpython_do \
 	plpython_global \
 	plpython_import \