diff --git a/internal/distributed/proxy/httpserver/handler_v2.go b/internal/distributed/proxy/httpserver/handler_v2.go
index 69402f9f1be9e..1cdc27c53f995 100644
--- a/internal/distributed/proxy/httpserver/handler_v2.go
+++ b/internal/distributed/proxy/httpserver/handler_v2.go
@@ -964,9 +964,13 @@ func (h *HandlersV2) search(ctx context.Context, c *gin.Context, anyReq any, dbN
 	searchParams := generateSearchParams(ctx, c, httpReq.SearchParams)
 	searchParams = append(searchParams, &commonpb.KeyValuePair{Key: common.TopKKey, Value: strconv.FormatInt(int64(httpReq.Limit), 10)})
 	searchParams = append(searchParams, &commonpb.KeyValuePair{Key: ParamOffset, Value: strconv.FormatInt(int64(httpReq.Offset), 10)})
-	searchParams = append(searchParams, &commonpb.KeyValuePair{Key: ParamGroupByField, Value: httpReq.GroupByField})
-	searchParams = append(searchParams, &commonpb.KeyValuePair{Key: ParamGroupSize, Value: strconv.FormatInt(int64(httpReq.GroupSize), 10)})
-	searchParams = append(searchParams, &commonpb.KeyValuePair{Key: ParamGroupStrictSize, Value: strconv.FormatBool(httpReq.GroupStrictSize)})
+	if httpReq.GroupByField != "" {
+		searchParams = append(searchParams, &commonpb.KeyValuePair{Key: ParamGroupByField, Value: httpReq.GroupByField})
+	}
+	if httpReq.GroupByField != "" && httpReq.GroupSize > 0 {
+		searchParams = append(searchParams, &commonpb.KeyValuePair{Key: ParamGroupSize, Value: strconv.FormatInt(int64(httpReq.GroupSize), 10)})
+		searchParams = append(searchParams, &commonpb.KeyValuePair{Key: ParamGroupStrictSize, Value: strconv.FormatBool(httpReq.GroupStrictSize)})
+	}
 	searchParams = append(searchParams, &commonpb.KeyValuePair{Key: proxy.AnnsFieldKey, Value: httpReq.AnnsField})
 	body, _ := c.Get(gin.BodyBytesKey)
 	placeholderGroup, err := generatePlaceholderGroup(ctx, string(body.([]byte)), collSchema, httpReq.AnnsField)
@@ -1064,9 +1068,13 @@ func (h *HandlersV2) advancedSearch(ctx context.Context, c *gin.Context, anyReq
 		{Key: proxy.RankParamsKey, Value: string(bs)},
 		{Key: ParamLimit, Value: strconv.FormatInt(int64(httpReq.Limit), 10)},
 		{Key: ParamRoundDecimal, Value: "-1"},
-		{Key: ParamGroupByField, Value: httpReq.GroupByField},
-		{Key: ParamGroupSize, Value: strconv.FormatInt(int64(httpReq.GroupSize), 10)},
-		{Key: ParamGroupStrictSize, Value: strconv.FormatBool(httpReq.GroupStrictSize)},
+	}
+	if httpReq.GroupByField != "" {
+		req.RankParams = append(req.RankParams, &commonpb.KeyValuePair{Key: ParamGroupByField, Value: httpReq.GroupByField})
+	}
+	if httpReq.GroupByField != "" && httpReq.GroupSize > 0 {
+		req.RankParams = append(req.RankParams, &commonpb.KeyValuePair{Key: ParamGroupSize, Value: strconv.FormatInt(int64(httpReq.GroupSize), 10)})
+		req.RankParams = append(req.RankParams, &commonpb.KeyValuePair{Key: ParamGroupStrictSize, Value: strconv.FormatBool(httpReq.GroupStrictSize)})
 	}
 	resp, err := wrapperProxyWithLimit(ctx, c, req, h.checkAuth, false, "/milvus.proto.milvus.MilvusService/HybridSearch", true, h.proxy, func(reqCtx context.Context, req any) (interface{}, error) {
 		return h.proxy.HybridSearch(reqCtx, req.(*milvuspb.HybridSearchRequest))
diff --git a/internal/proxy/search_util.go b/internal/proxy/search_util.go
index 116d8b656a4af..2d873a23dafca 100644
--- a/internal/proxy/search_util.go
+++ b/internal/proxy/search_util.go
@@ -370,8 +370,15 @@ func parseGroupByInfo(searchParamsPair []*commonpb.KeyValuePair, schema *schemap
 		groupSize = 1
 	} else {
 		groupSize, err = strconv.ParseInt(groupSizeStr, 0, 64)
-		if err != nil || groupSize <= 0 {
-			groupSize = 1
+		if err != nil {
+			ret.err = merr.WrapErrParameterInvalidMsg(
+				fmt.Sprintf("failed to parse input group size:%s", groupSizeStr))
+			return ret
+		}
+		if groupSize <= 0 {
+			ret.err = merr.WrapErrParameterInvalidMsg(
+				fmt.Sprintf("input group size:%d is negative, failed to do search_groupby", groupSize))
+			return ret
 		}
 	}
 	if groupSize > Params.QuotaConfig.MaxGroupSize.GetAsInt64() {
diff --git a/internal/proxy/task_search_test.go b/internal/proxy/task_search_test.go
index b0b0e77d954d7..9ed4a03f27dec 100644
--- a/internal/proxy/task_search_test.go
+++ b/internal/proxy/task_search_test.go
@@ -2538,7 +2538,7 @@ func TestTaskSearch_parseSearchInfo(t *testing.T) {
 		assert.Equal(t, Params.QuotaConfig.TopKLimit.GetAsInt64(), searchInfo.planInfo.GetTopk())
 	})
 
-	t.Run("check max group size", func(t *testing.T) {
+	t.Run("check correctness of group size", func(t *testing.T) {
 		normalParam := getValidSearchParams()
 		normalParam = append(normalParam, &commonpb.KeyValuePair{
 			Key:   GroupSizeKey,
@@ -2553,14 +2553,26 @@ func TestTaskSearch_parseSearchInfo(t *testing.T) {
 			Fields: fields,
 		}
 		searchInfo := parseSearchInfo(normalParam, schema, nil)
-		assert.Nil(t, searchInfo.planInfo)
 		assert.Error(t, searchInfo.parseError)
 		assert.True(t, strings.Contains(searchInfo.parseError.Error(), "exceeds configured max group size"))
-
-		resetSearchParamsValue(normalParam, GroupSizeKey, `10`)
-		searchInfo = parseSearchInfo(normalParam, schema, nil)
-		assert.NotNil(t, searchInfo.planInfo)
-		assert.NoError(t, searchInfo.parseError)
+		{
+			resetSearchParamsValue(normalParam, GroupSizeKey, `10`)
+			searchInfo = parseSearchInfo(normalParam, schema, nil)
+			assert.NoError(t, searchInfo.parseError)
+			assert.Equal(t, int64(10), searchInfo.planInfo.GroupSize)
+		}
+		{
+			resetSearchParamsValue(normalParam, GroupSizeKey, `-1`)
+			searchInfo = parseSearchInfo(normalParam, schema, nil)
+			assert.Error(t, searchInfo.parseError)
+			assert.True(t, strings.Contains(searchInfo.parseError.Error(), "is negative"))
+		}
+		{
+			resetSearchParamsValue(normalParam, GroupSizeKey, `xxx`)
+			searchInfo = parseSearchInfo(normalParam, schema, nil)
+			assert.Error(t, searchInfo.parseError)
+			assert.True(t, strings.Contains(searchInfo.parseError.Error(), "failed to parse input group size"))
+		}
 	})
 }