diff --git a/server/internal/exporter/stream.go b/server/internal/exporter/stream.go
index 639eb8b..32d598c 100644
--- a/server/internal/exporter/stream.go
+++ b/server/internal/exporter/stream.go
@@ -203,22 +203,31 @@ func CountRowsFastChunked(db *sql.DB, ds, main string, filters map[string]interf
 		return CountRowsFast(db, ds, main, filters)
 	}
 	daysDiff := int(en.Sub(st).Hours() / 24)
-	
-	// 如果时间跨度超过 15 天（半个月），使用按周分片（7天），否则使用按天分片（15天）
+
+	// 优化：根据时间跨度自适应分块策略
+	// ≤15天: 直接查询，≤30天: 按天分片，>30天: 按月分片（30天）
 	var ranges [][2]string
-	if daysDiff > 15 {
+	if daysDiff <= 15 {
+		// 15天内直接查询，不分片
+		return CountRowsFast(db, ds, main, filters)
+	} else if daysDiff <= 30 {
+		// 15-30天：按天分片（步长15）
+		ranges = SplitByDays(start, end, 15)
+	} else if daysDiff <= 90 {
+		// 30-90天：按周分片（7天）
 		ranges = SplitByWeeks(start, end)
+	} else {
+		// >90天：按月分片（30天）
+		ranges = SplitByMonths(start, end)
 		logging.JSON("INFO", map[string]interface{}{
-			"event":      "count_chunked_by_weeks",
+			"event":      "count_chunked_by_months",
 			"datasource": ds,
 			"main":       main,
 			"days_diff":  daysDiff,
 			"chunks":     len(ranges),
 		})
-	} else {
-		ranges = SplitByDays(start, end, 15)
 	}
-	
+
 	var total int64
 	for _, rg := range ranges {
 		fl := map[string]interface{}{}
@@ -279,6 +288,31 @@ func SplitByWeeks(startStr, endStr string) [][2]string {
 	return out
 }
 
+// SplitByMonths 按月（30天）分割时间范围，用于超長时间跨度的分块統計
+func SplitByMonths(startStr, endStr string) [][2]string {
+	layout := "2006-01-02 15:04:05"
+	s := strings.TrimSpace(startStr)
+	e := strings.TrimSpace(endStr)
+	st, err1 := time.Parse(layout, s)
+	en, err2 := time.Parse(layout, e)
+	if err1 != nil || err2 != nil || !en.After(st) {
+		return [][2]string{{s, e}}
+	}
+	var out [][2]string
+	cur := st
+	// 按月分片
+	for cur.Before(en) {
+		// 下个月的第一天
+		nxt := time.Date(cur.Year(), cur.Month()+1, 1, 0, 0, 0, 0, cur.Location())
+		if nxt.After(en) {
+			nxt = en
+		}
+		out = append(out, [2]string{cur.Format(layout), nxt.Format(layout)})
+		cur = nxt
+	}
+	return out
+}
+
 type RowTransform func([]string) []string
 type RollCallback func(path string, size int64, partRows int64) error
 type ProgressCallback func(totalRows int64) error