diff --git a/fe/fe-core/src/main/java/org/apache/doris/planner/OlapScanNode.java b/fe/fe-core/src/main/java/org/apache/doris/planner/OlapScanNode.java
index 6f814653dd4bec..143c175095d82e 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/planner/OlapScanNode.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/planner/OlapScanNode.java
@@ -794,15 +794,27 @@ private void filterDeletedRows(Analyzer analyzer) throws AnalysisException {
         }
     }
 
+    /*
+    Although sometimes the scan range only involves one instance,
+        the data distribution cannot be set to UNPARTITION here.
+    The reason is that @coordicator will not set the scan range for the fragment,
+        when data partition of fragment is UNPARTITION.
+     */
     public DataPartition constructInputPartitionByDistributionInfo() {
-        DistributionInfo distributionInfo = olapTable.getDefaultDistributionInfo();
-        Preconditions.checkState(distributionInfo instanceof HashDistributionInfo);
-        List<Column> distributeColumns = ((HashDistributionInfo) distributionInfo).getDistributionColumns();
-        List<Expr> dataDistributeExprs = Lists.newArrayList();
-        for (Column column : distributeColumns) {
-            SlotRef slotRef = new SlotRef(desc.getRef().getName(), column.getName());
-            dataDistributeExprs.add(slotRef);
-        }
-        return DataPartition.hashPartitioned(dataDistributeExprs);
+        if (Catalog.getCurrentColocateIndex().isColocateTable(olapTable.getId())
+                || olapTable.getPartitionInfo().getType() == PartitionType.UNPARTITIONED
+                || olapTable.getPartitions().size() == 1) {
+            DistributionInfo distributionInfo = olapTable.getDefaultDistributionInfo();
+            Preconditions.checkState(distributionInfo instanceof HashDistributionInfo);
+            List<Column> distributeColumns = ((HashDistributionInfo) distributionInfo).getDistributionColumns();
+            List<Expr> dataDistributeExprs = Lists.newArrayList();
+            for (Column column : distributeColumns) {
+                SlotRef slotRef = new SlotRef(desc.getRef().getName(), column.getName());
+                dataDistributeExprs.add(slotRef);
+            }
+            return DataPartition.hashPartitioned(dataDistributeExprs);
+        } else {
+            return DataPartition.RANDOM;
+        }
     }
 }
diff --git a/fe/fe-core/src/test/java/org/apache/doris/planner/ColocatePlanTest.java b/fe/fe-core/src/test/java/org/apache/doris/planner/ColocatePlanTest.java
index 5c28b224f3d042..a2fd126c14ac0b 100644
--- a/fe/fe-core/src/test/java/org/apache/doris/planner/ColocatePlanTest.java
+++ b/fe/fe-core/src/test/java/org/apache/doris/planner/ColocatePlanTest.java
@@ -50,8 +50,14 @@ public static void setUp() throws Exception {
         // create table test_colocate (k1 int ,k2 int, k3 int, k4 int)
         // distributed by hash(k1, k2) buckets 10
         // properties ("replication_num" = "2");
-        String createTblStmtStr = "create table db1.test_colocate(k1 int, k2 int, k3 int, k4 int) "
-                + "distributed by hash(k1, k2) buckets 10 properties('replication_num' = '2');";
+        String createColocateTblStmtStr = "create table db1.test_colocate(k1 int, k2 int, k3 int, k4 int) "
+                + "distributed by hash(k1, k2) buckets 10 properties('replication_num' = '2',"
+                + "'colocate_with' = 'group1');";
+        CreateTableStmt createColocateTableStmt = (CreateTableStmt) UtFrameUtils.parseAndAnalyzeStmt(createColocateTblStmtStr, ctx);
+        Catalog.getCurrentCatalog().createTable(createColocateTableStmt);
+        String createTblStmtStr = "create table db1.test(k1 int, k2 int, k3 int, k4 int)"
+                + "partition by range(k1) (partition p1 values less than (\"1\"), partition p2 values less than (\"2\"))"
+                + "distributed by hash(k1, k2) buckets 10 properties('replication_num' = '2')";
         CreateTableStmt createTableStmt = (CreateTableStmt) UtFrameUtils.parseAndAnalyzeStmt(createTblStmtStr, ctx);
         Catalog.getCurrentCatalog().createTable(createTableStmt);
     }
@@ -118,4 +124,17 @@ public void sqlAggMoreThanTableMeta() throws Exception {
         Assert.assertEquals(1, StringUtils.countMatches(plan1, "AGGREGATE"));
         Assert.assertTrue(plan1.contains(COLOCATE_ENABLE));
     }
+
+    // without:
+    // 1. agg columns = distributed columns
+    // 2. table is not in colocate group
+    // 3. more then 1 instances
+    // Fixed #6028
+    @Test
+    public void sqlAggWithNonColocateTable() throws Exception {
+        String sql = "explain select k1, k2 from db1.test group by k1, k2";
+        String plan1 = UtFrameUtils.getSQLPlanOrErrorMsg(ctx, sql);
+        Assert.assertEquals(2, StringUtils.countMatches(plan1, "AGGREGATE"));
+        Assert.assertFalse(plan1.contains(COLOCATE_ENABLE));
+    }
 }
diff --git a/fe/fe-core/src/test/java/org/apache/doris/planner/QueryPlanTest.java b/fe/fe-core/src/test/java/org/apache/doris/planner/QueryPlanTest.java
index a026992f582092..1edd790acab230 100644
--- a/fe/fe-core/src/test/java/org/apache/doris/planner/QueryPlanTest.java
+++ b/fe/fe-core/src/test/java/org/apache/doris/planner/QueryPlanTest.java
@@ -1359,7 +1359,7 @@ public void testAggregateSatisfyOlapTableDistribution() throws Exception {
         sql = "SELECT dt, dis_key, COUNT(1) FROM table_partitioned  group by dt, dis_key";
         explainString = UtFrameUtils.getSQLPlanOrErrorMsg(connectContext, "EXPLAIN " + sql);
         System.out.println(explainString);
-        Assert.assertTrue(explainString.contains("AGGREGATE (update finalize)"));
+        Assert.assertTrue(explainString.contains("AGGREGATE (update serialize)"));
     }
 
     public void testLeadAndLagFunction() throws Exception {