diff --git a/rc-service/rc-service-order/order-application/src/main/java/com/red/circle/order/app/common/V5PayOrderNumber.java b/rc-service/rc-service-order/order-application/src/main/java/com/red/circle/order/app/common/V5PayOrderNumber.java
index 03db259e..b28e9548 100644
--- a/rc-service/rc-service-order/order-application/src/main/java/com/red/circle/order/app/common/V5PayOrderNumber.java
+++ b/rc-service/rc-service-order/order-application/src/main/java/com/red/circle/order/app/common/V5PayOrderNumber.java
@@ -43,11 +43,13 @@ public final class V5PayOrderNumber {
   }
 
   private static String normalizedPrefix(String prefix) {
-    String normalized = Objects.toString(prefix, "").trim().toUpperCase(Locale.ROOT);
-    if (StringUtils.isBlank(normalized) || !isAsciiLettersOrDigits(normalized)) {
+    String rawPrefix = Objects.toString(prefix, "").trim();
+    // 无分隔符拼接时，前缀若包含数字会产生命名空间碰撞，例如 YUMI+123 与 YUMI1+23；
+    // 必须在大小写转换前校验 ASCII，避免 Unicode 字母（如 dotless i）转换成 ASCII 后绕过限制。
+    if (StringUtils.isBlank(rawPrefix) || !isAsciiLetters(rawPrefix)) {
       throw new IllegalArgumentException("V5Pay order prefix is invalid");
     }
-    return normalized;
+    return rawPrefix.toUpperCase(Locale.ROOT);
   }
 
   private static boolean isAsciiDigits(String value) {
@@ -60,11 +62,11 @@ public final class V5PayOrderNumber {
     return true;
   }
 
-  private static boolean isAsciiLettersOrDigits(String value) {
+  private static boolean isAsciiLetters(String value) {
     for (int index = 0; index < value.length(); index++) {
       char item = value.charAt(index);
       boolean letter = (item >= 'A' && item <= 'Z') || (item >= 'a' && item <= 'z');
-      if (!letter && (item < '0' || item > '9')) {
+      if (!letter) {
         return false;
       }
     }
diff --git a/rc-service/rc-service-order/order-application/src/test/java/com/red/circle/order/app/common/V5PayOrderNumberTest.java b/rc-service/rc-service-order/order-application/src/test/java/com/red/circle/order/app/common/V5PayOrderNumberTest.java
index 5ea0901d..c3b1afae 100644
--- a/rc-service/rc-service-order/order-application/src/test/java/com/red/circle/order/app/common/V5PayOrderNumberTest.java
+++ b/rc-service/rc-service-order/order-application/src/test/java/com/red/circle/order/app/common/V5PayOrderNumberTest.java
@@ -48,6 +48,19 @@ public class V5PayOrderNumberTest {
     assertIllegalArgument(() -> V5PayOrderNumber.providerOrderNo("YUMI", -1L));
   }
 
+  @Test
+  public void rejectsDigitBearingPrefixesThatCouldCollideWithoutSeparator() {
+    assertEquals("YUMI123", V5PayOrderNumber.providerOrderNo("YUMI", 123L));
+
+    // YUMI1 + 23 会与合法的 YUMI + 123 生成同一个三方单号，因此数字不能出现在前缀任意位置。
+    assertIllegalArgument(() -> V5PayOrderNumber.providerOrderNo("YUMI1", 23L));
+    assertIllegalArgument(() -> V5PayOrderNumber.localOrderId("YUMI1", "YUMI123"));
+    assertIllegalArgument(() -> V5PayOrderNumber.providerOrderNo("1YUMI", 23L));
+    assertIllegalArgument(() -> V5PayOrderNumber.providerOrderNo("YU1MI", 23L));
+    assertIllegalArgument(() -> V5PayOrderNumber.providerOrderNo("123", 23L));
+    assertIllegalArgument(() -> V5PayOrderNumber.providerOrderNo("yumı", 23L));
+  }
+
   private void assertIllegalArgument(Runnable action) {
     try {
       action.run();