diff --git a/hutool-core/src/main/java/cn/hutool/core/util/RandomUtil.java b/hutool-core/src/main/java/cn/hutool/core/util/RandomUtil.java
index 8d77384e7..3e1db16a0 100644
--- a/hutool-core/src/main/java/cn/hutool/core/util/RandomUtil.java
+++ b/hutool-core/src/main/java/cn/hutool/core/util/RandomUtil.java
@@ -14,13 +14,7 @@ import java.math.BigDecimal;
 import java.math.RoundingMode;
 import java.security.NoSuchAlgorithmException;
 import java.security.SecureRandom;
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Date;
-import java.util.LinkedHashSet;
-import java.util.List;
-import java.util.Random;
-import java.util.Set;
+import java.util.*;
 import java.util.concurrent.ThreadLocalRandom;
 
 /**
@@ -524,7 +518,7 @@ public class RandomUtil {
 	 */
 	public static String randomStringWithoutStr(int length, String elemData) {
 		String baseStr = BASE_CHAR_NUMBER;
-		baseStr = StrUtil.removeAll(baseStr, elemData.toCharArray());
+		baseStr = StrUtil.removeAll(baseStr, elemData.toLowerCase(Locale.ROOT).toCharArray());
 		return randomString(baseStr, length);
 	}
 
diff --git a/hutool-core/src/test/java/cn/hutool/core/util/RandomUtilTest.java b/hutool-core/src/test/java/cn/hutool/core/util/RandomUtilTest.java
index 978fcd2ed..1472dcd79 100644
--- a/hutool-core/src/test/java/cn/hutool/core/util/RandomUtilTest.java
+++ b/hutool-core/src/test/java/cn/hutool/core/util/RandomUtilTest.java
@@ -8,6 +8,7 @@ import org.junit.Test;
 
 import java.math.RoundingMode;
 import java.util.List;
+import java.util.Locale;
 import java.util.Set;
 
 public class RandomUtilTest {
@@ -59,4 +60,14 @@ public class RandomUtilTest {
 		char c = RandomUtil.randomChinese();
 		Assert.assertTrue(c > 0);
 	}
+	@Test
+	public void randomStringWithoutStrTest() {
+		for (int i = 0; i < 100; i++) {
+			final String s = RandomUtil.randomStringWithoutStr(8, "0IPOL");
+			System.out.println(s);
+			for (char c : "0IPOL".toCharArray()) {
+				Assert.assertFalse(s.contains((String.valueOf(c).toLowerCase(Locale.ROOT))));
+			}
+		}
+	}
 }