diff --git a/src/gausskernel/optimizer/commands/tablecmds.cpp b/src/gausskernel/optimizer/commands/tablecmds.cpp
index 721eb8b5d..88e3c4214 100755
--- a/src/gausskernel/optimizer/commands/tablecmds.cpp
+++ b/src/gausskernel/optimizer/commands/tablecmds.cpp
@@ -13806,6 +13806,7 @@ static ObjectAddress ATExecDropNotNull(Relation rel, const char* colName, LOCKMO
     List* indexoidlist = NIL;
     ListCell* indexoidscan = NULL;
     ObjectAddress address;
+    Oid replidindex;
 
     /*
      * lookup the attribute
@@ -13833,6 +13834,9 @@ static ObjectAddress ATExecDropNotNull(Relation rel, const char* colName, LOCKMO
     /* Loop over all indexes on the relation */
     indexoidlist = RelationGetIndexList(rel);
 
+    /* replica identity index */
+    replidindex = rel->rd_replidindex;
+
     foreach (indexoidscan, indexoidlist) {
         Oid indexoid = lfirst_oid(indexoidscan);
         HeapTuple indexTuple;
@@ -13863,6 +13867,16 @@ static ObjectAddress ATExecDropNotNull(Relation rel, const char* colName, LOCKMO
             }
         }
 
+        /* REPLICA IDENTIFY can't drop not null */
+        if (replidindex == indexoid) {
+            for (i = 0; i < indnkeyatts; i++) {
+                if (indexStruct->indkey.values[i] == attnum)
+                    ereport(ERROR,
+                        (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
+                            errmsg("column \"%s\" used as replica identity can't drop not null", colName)));
+            }
+        }
+
         ReleaseSysCache(indexTuple);
     }
 
diff --git a/src/test/regress/expected/replica_identity.out b/src/test/regress/expected/replica_identity.out
index ab2698531..ab27a6101 100644
--- a/src/test/regress/expected/replica_identity.out
+++ b/src/test/regress/expected/replica_identity.out
@@ -80,6 +80,13 @@ SELECT count(*) FROM pg_index WHERE indrelid = 'test_replica_identity'::regclass
      1
 (1 row)
 
+----
+-- Make sure can't alter replica identity index alown NULL
+----
+CREATE UNIQUE INDEX uni_idx_keya ON test_replica_identity (keya);
+ALTER TABLE test_replica_identity REPLICA IDENTITY USING INDEX uni_idx_keya;
+ALTER TABLE test_replica_identity MODIFY keya NULL;  -- fail
+ERROR:  column "keya" used as replica identity can't drop not null
 ----
 -- Make sure non index cases work
 ----
@@ -113,6 +120,7 @@ SELECT relreplident FROM pg_class WHERE oid = 'test_replica_identity'::regclass;
  nonkey | text    | 
 Indexes:
     "test_replica_identity_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default
+    "uni_idx_keya" UNIQUE, btree (keya) TABLESPACE pg_default
     "test_replica_identity_hash" hash (nonkey) TABLESPACE pg_default
     "test_replica_identity_keyab" btree (keya, keyb) TABLESPACE pg_default
 Replica Identity: FULL
diff --git a/src/test/regress/sql/replica_identity.sql b/src/test/regress/sql/replica_identity.sql
index 0bdbfb17e..6565ef329 100644
--- a/src/test/regress/sql/replica_identity.sql
+++ b/src/test/regress/sql/replica_identity.sql
@@ -41,6 +41,13 @@ SELECT relreplident FROM pg_class WHERE oid = 'test_replica_identity'::regclass;
 
 SELECT count(*) FROM pg_index WHERE indrelid = 'test_replica_identity'::regclass AND indisreplident;
 
+----
+-- Make sure can't alter replica identity index alown NULL
+----
+CREATE UNIQUE INDEX uni_idx_keya ON test_replica_identity (keya);
+ALTER TABLE test_replica_identity REPLICA IDENTITY USING INDEX uni_idx_keya;
+ALTER TABLE test_replica_identity MODIFY keya NULL;  -- fail
+
 ----
 -- Make sure non index cases work
 ----