diff --git a/plugin-default-impl/src/main/java/com/alibaba/nacos/plugin/auth/impl/jwt/NacosJwtParser.java b/plugin-default-impl/src/main/java/com/alibaba/nacos/plugin/auth/impl/jwt/NacosJwtParser.java
index 1bad56dad7c..4adfa6f3ec0 100644
--- a/plugin-default-impl/src/main/java/com/alibaba/nacos/plugin/auth/impl/jwt/NacosJwtParser.java
+++ b/plugin-default-impl/src/main/java/com/alibaba/nacos/plugin/auth/impl/jwt/NacosJwtParser.java
@@ -18,11 +18,10 @@
 
 import com.alibaba.nacos.plugin.auth.exception.AccessException;
 import com.alibaba.nacos.plugin.auth.impl.users.NacosUser;
+import com.alibaba.nacos.plugin.auth.impl.utils.Base64Decode;
 
 import javax.crypto.spec.SecretKeySpec;
-import java.nio.charset.StandardCharsets;
 import java.security.Key;
-import java.util.Base64;
 import java.util.concurrent.TimeUnit;
 
 /**
@@ -39,13 +38,7 @@ public class NacosJwtParser {
     private final Key key;
     
     public NacosJwtParser(String base64edKey) {
-        byte[] decode;
-        try {
-            decode = Base64.getDecoder().decode(base64edKey);
-        } catch (IllegalArgumentException e) {
-            decode = base64edKey.getBytes(StandardCharsets.US_ASCII);
-        }
-        
+        byte[] decode = Base64Decode.decode(base64edKey);
         int bitLength = decode.length << 3;
         if (bitLength < 256) {
             String msg = "The specified key byte array is " + bitLength + " bits which "
diff --git a/plugin-default-impl/src/main/java/com/alibaba/nacos/plugin/auth/impl/utils/Base64Decode.java b/plugin-default-impl/src/main/java/com/alibaba/nacos/plugin/auth/impl/utils/Base64Decode.java
new file mode 100644
index 00000000000..d09be2dee01
--- /dev/null
+++ b/plugin-default-impl/src/main/java/com/alibaba/nacos/plugin/auth/impl/utils/Base64Decode.java
@@ -0,0 +1,132 @@
+/*
+ * Copyright 1999-2022 Alibaba Group Holding Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.alibaba.nacos.plugin.auth.impl.utils;
+
+import java.util.Arrays;
+
+/**
+ * Base64Decoder.
+ *
+ * @author xYohn
+ * @date 2023/8/7
+ */
+public class Base64Decode {
+    private static final char[] BASE64_ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();
+
+    private static final int[] BASE64_IALPHABET = new int[256];
+
+    private static final int IALPHABET_MAX_INDEX = BASE64_IALPHABET.length - 1;
+
+    private static final int[] IALPHABET = BASE64_IALPHABET;
+
+    static {
+        Arrays.fill(BASE64_IALPHABET, -1);
+        for (int i = 0, iS = BASE64_ALPHABET.length; i < iS; i++) {
+            BASE64_IALPHABET[BASE64_ALPHABET[i]] = i;
+        }
+        BASE64_IALPHABET['='] = 0;
+    }
+
+    /**
+     * Decodes a Base64 encoded String into a newly-allocated byte array using the Base64 encoding scheme.
+     *
+     * @param input the string to decode
+     * @return a byte array containing binary data
+     */
+    public static byte[] decode(String input) {
+
+        // Check special case
+        if (input == null || input.equals("")) {
+            return new byte[0];
+        }
+        char[] sArr = input.toCharArray();
+        int sLen = sArr.length;
+        if (sLen == 0) {
+            return new byte[0];
+        }
+
+        int sIx = 0;
+        // Start and end index after trimming.
+        int eIx = sLen - 1;
+
+        // Trim illegal chars from start
+        while (sIx < eIx && IALPHABET[sArr[sIx]] < 0) {
+            sIx++;
+        }
+
+        // Trim illegal chars from end
+        while (eIx > 0 && IALPHABET[sArr[eIx]] < 0) {
+            eIx--;
+        }
+
+        // get the padding count (=) (0, 1 or 2)
+        // Count '=' at end.
+        int pad = sArr[eIx] == '=' ? (sArr[eIx - 1] == '=' ? 2 : 1) : 0;
+        // Content count including possible separators
+        int cCnt = eIx - sIx + 1;
+        int sepCnt = sLen > 76 ? (sArr[76] == '\r' ? cCnt / 78 : 0) << 1 : 0;
+        // The number of decoded bytes
+        int len = ((cCnt - sepCnt) * 6 >> 3) - pad;
+        // Preallocate byte[] of exact length
+        byte[] dArr = new byte[len];
+
+        // Decode all but the last 0 - 2 bytes.
+        int d = 0;
+        int three = 3;
+        int eight = 8;
+        for (int cc = 0, eLen = (len / three) * three; d < eLen; ) {
+
+            // Assemble three bytes into an int from four "valid" characters.
+            int i = ctoi(sArr[sIx++]) << 18 | ctoi(sArr[sIx++]) << 12 | ctoi(sArr[sIx++]) << 6 | ctoi(sArr[sIx++]);
+
+            // Add the bytes
+            dArr[d++] = (byte) (i >> 16);
+            dArr[d++] = (byte) (i >> 8);
+            dArr[d++] = (byte) i;
+
+            // If line separator, jump over it.
+            if (sepCnt > 0 && ++cc == 19) {
+                sIx += 2;
+                cc = 0;
+            }
+        }
+
+        if (d < len) {
+            // Decode last 1-3 bytes (incl '=') into 1-3 bytes
+            int i = 0;
+            for (int j = 0; sIx <= eIx - pad; j++) {
+                i |= ctoi(sArr[sIx++]) << (18 - j * 6);
+            }
+
+            for (int r = 16; d < len; r -= eight) {
+                dArr[d++] = (byte) (i >> r);
+            }
+        }
+
+        return dArr;
+    }
+
+    private static int ctoi(char c) {
+        int i = c > IALPHABET_MAX_INDEX ? -1 : IALPHABET[c];
+        if (i < 0) {
+            String msg = "Illegal base64 character: '" + c + "'";
+            throw new IllegalArgumentException(msg);
+        }
+        return i;
+    }
+
+}
diff --git a/plugin-default-impl/src/test/java/com/alibaba/nacos/plugin/auth/impl/utils/Base64DecodeTest.java b/plugin-default-impl/src/test/java/com/alibaba/nacos/plugin/auth/impl/utils/Base64DecodeTest.java
new file mode 100644
index 00000000000..e46499a10c4
--- /dev/null
+++ b/plugin-default-impl/src/test/java/com/alibaba/nacos/plugin/auth/impl/utils/Base64DecodeTest.java
@@ -0,0 +1,45 @@
+/*
+ * Copyright 1999-2021 Alibaba Group Holding Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.alibaba.nacos.plugin.auth.impl.utils;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Base64Decoder test.
+ *
+ * @author xYohn
+ * @date 2023/8/8
+ */
+public class Base64DecodeTest {
+    @Test
+    public void testStandardDecode() {
+        String origin = "aGVsbG8sbmFjb3MhdGVzdEJhc2U2NGVuY29kZQ==";
+        String expectDecodeOrigin = "hello,nacos!testBase64encode";
+        byte[] decodeOrigin = Base64Decode.decode(origin);
+        Assert.assertArrayEquals(decodeOrigin, expectDecodeOrigin.getBytes());
+    }
+
+    @Test
+    public void testNotStandardDecode() {
+        String notStandardOrigin = "SecretKey012345678901234567890123456789012345678901234567890123456789";
+        byte[] decodeNotStandardOrigin = Base64Decode.decode(notStandardOrigin);
+        String truncationOrigin = "SecretKey01234567890123456789012345678901234567890123456789012345678";
+        byte[] decodeTruncationOrigin = Base64Decode.decode(truncationOrigin);
+        Assert.assertArrayEquals(decodeNotStandardOrigin, decodeTruncationOrigin);
+    }
+}