diff --git a/src/actions/snapshots.ts b/src/actions/snapshots.ts
index 7d9c2d5..d221db8 100644
--- a/src/actions/snapshots.ts
+++ b/src/actions/snapshots.ts
@@ -4,6 +4,7 @@ import { db } from '@/db';
 import { portfolioSnapshots } from '@/db/schema';
 import { getPortfolioPositions } from './portfolio';
 import { eq, sql } from 'drizzle-orm';
+import Big from 'big.js';
 
 function getTodayInShanghai(): string {
   const now = new Date();
@@ -22,13 +23,13 @@ export async function recordDailySnapshot() {
 
   const totalValueCny = positions.reduce(
     (sum, pos) => sum.plus(pos.cnyValue || '0'),
-    0 as number | string
-  );
+    new Big(0)
+  ).toString();
 
   const totalCostCny = positions.reduce(
     (sum, pos) => sum.plus(pos.totalCostCny || '0'),
-    0 as number | string
-  );
+    new Big(0)
+  ).toString();
 
   const dateStr = getTodayInShanghai();
 
@@ -44,8 +45,8 @@ export async function recordDailySnapshot() {
     await db
       .update(portfolioSnapshots)
       .set({
-        totalValueCny: String(totalValueCny),
-        totalCostCny: String(totalCostCny),
+        totalValueCny,
+        totalCostCny,
         updatedAt: now,
       })
       .where(eq(portfolioSnapshots.date, dateStr));
@@ -54,8 +55,8 @@ export async function recordDailySnapshot() {
       success: true,
       action: 'updated',
       date: dateStr,
-      totalValueCny: String(totalValueCny),
-      totalCostCny: String(totalCostCny),
+      totalValueCny,
+      totalCostCny,
     };
   }
 
@@ -63,8 +64,8 @@ export async function recordDailySnapshot() {
     .insert(portfolioSnapshots)
     .values({
       date: dateStr,
-      totalValueCny: String(totalValueCny),
-      totalCostCny: String(totalCostCny),
+      totalValueCny,
+      totalCostCny,
       createdAt: now,
       updatedAt: now,
     });
@@ -73,8 +74,8 @@ export async function recordDailySnapshot() {
     success: true,
     action: 'inserted',
     date: dateStr,
-    totalValueCny: String(totalValueCny),
-    totalCostCny: String(totalCostCny),
+    totalValueCny,
+    totalCostCny,
   };
 }