diff --git a/apps/admin/src/sections/lottery/prize-form.tsx b/apps/admin/src/sections/lottery/prize-form.tsx
index 1a1a1e9..0eb487d 100644
--- a/apps/admin/src/sections/lottery/prize-form.tsx
+++ b/apps/admin/src/sections/lottery/prize-form.tsx
@@ -43,6 +43,8 @@ import { toast } from "sonner";
 import { z } from "zod";
 
 const CENTS_PER_YUAN = 100;
+// 概率单位约定：weight 1000 = 1%（支持 3 位小数概率，总权重 100000 = 100%）。
+const WEIGHT_PER_PERCENT = 1000;
 
 type TranslateFn = (key: string, defaultValue: string) => string;
 
@@ -102,7 +104,6 @@ const getPrizeSchema = (t: TranslateFn) =>
         .optional(),
       weight: z
         .number()
-        .int(t("prize.weightInteger", "Probability must be an integer"))
         .min(0, t("prize.weightMin", "Probability must be at least 0"))
         .max(100, t("prize.weightMax", "Probability cannot exceed 100")),
       unlimited_stock: z.boolean(),
@@ -221,7 +222,7 @@ function toFormValues(prize?: API.LotteryPrize): PrizeFormValues {
     type: (prize?.type as PrizeFormValues["type"]) ?? "vpn_duration",
     name: prize?.name ?? "",
     icon_url: prize?.icon_url ?? "",
-    weight: prize?.weight ?? 1,
+    weight: (prize?.weight ?? 0) / WEIGHT_PER_PERCENT,
     unlimited_stock: prize ? prize.total_stock === null : true,
     total_stock: prize?.total_stock ?? undefined,
     is_fallback: prize?.is_fallback ?? false,
@@ -325,7 +326,9 @@ export default function PrizeForm({
         name: values.name.trim(),
         icon_url: values.icon_url?.trim() ?? "",
         config: toConfig(values),
-        weight: values.is_fallback ? 0 : values.weight,
+        weight: values.is_fallback
+          ? 0
+          : Math.round(values.weight * WEIGHT_PER_PERCENT),
         total_stock: values.unlimited_stock
           ? null
           : (values.total_stock ?? null),
@@ -643,7 +646,7 @@ export default function PrizeForm({
                   type: "number",
                   min: 0,
                   max: 100,
-                  step: 1,
+                  step: 0.001,
                   suffix: "%",
                   disabled: isFallback,
                 },
diff --git a/apps/admin/src/sections/lottery/prize-grid.tsx b/apps/admin/src/sections/lottery/prize-grid.tsx
index a5565a7..4bc9d01 100644
--- a/apps/admin/src/sections/lottery/prize-grid.tsx
+++ b/apps/admin/src/sections/lottery/prize-grid.tsx
@@ -14,9 +14,16 @@ import PrizeForm from "./prize-form";
 
 const DEFAULT_GRID_SIZE = 9;
 const CENTER_SLOT = 4;
-const PERCENT_DECIMALS = 1;
-const REQUIRED_TOTAL_PERCENT = 100;
 const CENTS_PER_YUAN = 100;
+// 概率单位约定：weight 1000 = 1%，总权重 100000 = 100.000%（支持 3 位小数概率）。
+const WEIGHT_PER_PERCENT = 1000;
+const FULL_TOTAL_WEIGHT = 100 * WEIGHT_PER_PERCENT;
+
+// weightToPercent 把原始 weight 转成百分比字符串（最多 3 位小数，去尾零）。
+function weightToPercent(weight: number): string {
+  const pct = weight / WEIGHT_PER_PERCENT;
+  return `${Number.parseFloat(pct.toFixed(3))}`;
+}
 
 interface PrizeGridProps {
   activity: API.LotteryActivity;
@@ -110,7 +117,7 @@ export default function PrizeGrid({ activity }: PrizeGridProps) {
     [randomPrizes]
   );
   const hasFallback = prizes.some((prize) => prize.is_fallback);
-  const totalIsValid = totalWeight === REQUIRED_TOTAL_PERCENT;
+  const totalIsValid = totalWeight === FULL_TOTAL_WEIGHT;
   const gridSize = activity.grid_size || DEFAULT_GRID_SIZE;
   const slots = Array.from({ length: gridSize }, (_, index) => index);
 
@@ -137,7 +144,8 @@ export default function PrizeGrid({ activity }: PrizeGridProps) {
           </p>
           {randomPrizes.length > 0 && (
             <Badge variant={totalIsValid ? "secondary" : "destructive"}>
-              {t("prize.probabilityTotal", "Total")}: {totalWeight}%
+              {t("prize.probabilityTotal", "Total")}:{" "}
+              {weightToPercent(totalWeight)}%
             </Badge>
           )}
         </div>
@@ -145,9 +153,7 @@ export default function PrizeGrid({ activity }: PrizeGridProps) {
           <div className="flex flex-wrap gap-2">
             {randomPrizes.map((prize) => (
               <Badge key={prize.id} variant="secondary">
-                {prize.name}:{" "}
-                {((prize.weight / totalWeight) * 100).toFixed(PERCENT_DECIMALS)}
-                %
+                {prize.name}: {weightToPercent(prize.weight)}%
               </Badge>
             ))}
           </div>
@@ -170,7 +176,7 @@ export default function PrizeGrid({ activity }: PrizeGridProps) {
             {t(
               "prize.totalNot100Hint",
               "The drawable prizes currently total {{total}}%. Adjust each prize's win probability so they sum to exactly 100%.",
-              { total: totalWeight }
+              { total: weightToPercent(totalWeight) }
             )}
           </AlertDescription>
         </Alert>
@@ -244,8 +250,10 @@ export default function PrizeGrid({ activity }: PrizeGridProps) {
                   })()}
                   <span className="text-muted-foreground text-xs">
                     {t("prize.weightShort", "Prob")}:{" "}
-                    {prize.is_fallback ? "—" : `${prize.weight}%`} ·{" "}
-                    {t("prize.stockShort", "Stock")}:{" "}
+                    {prize.is_fallback
+                      ? "—"
+                      : `${weightToPercent(prize.weight)}%`}{" "}
+                    · {t("prize.stockShort", "Stock")}:{" "}
                     {prize.total_stock === null ? "∞" : prize.total_stock}
                   </span>
                   <div className="flex flex-wrap justify-center gap-1">