diff --git a/FastGithub.DomainResolve/DnsClient.cs b/FastGithub.DomainResolve/DnsClient.cs
index 97ea09e..a734674 100644
--- a/FastGithub.DomainResolve/DnsClient.cs
+++ b/FastGithub.DomainResolve/DnsClient.cs
@@ -23,11 +23,10 @@ namespace FastGithub.DomainResolve
         /// DNS客户端
         /// </summary>
         /// <param name="dns"></param>
-        /// <param name="forceTcp"></param>
-        public DnsClient(IPEndPoint dns, bool forceTcp)
+        public DnsClient(IPEndPoint dns)
         {
             this.dns = dns;
-            this.resolver = forceTcp
+            this.resolver = dns.Port == 53
                 ? new TcpRequestResolver(dns)
                 : new UdpRequestResolver(dns, new TcpRequestResolver(dns));
         }
diff --git a/FastGithub.DomainResolve/DomainResolver.cs b/FastGithub.DomainResolve/DomainResolver.cs
index 3c8777d..f66ea7c 100644
--- a/FastGithub.DomainResolve/DomainResolver.cs
+++ b/FastGithub.DomainResolve/DomainResolver.cs
@@ -145,7 +145,7 @@ namespace FastGithub.DomainResolve
                 return null;
             }
 
-            var dnsClient = new DnsClient(dns, forceTcp: false);
+            var dnsClient = new DnsClient(dns);
             var address = await this.LookupAsync(dnsClient, domain, cancellationToken);
             return address ?? await this.LookupAsync(dnsClient, domain, cancellationToken);
         }
@@ -161,7 +161,7 @@ namespace FastGithub.DomainResolve
         {
             foreach (var dns in this.fastGithubConfig.FallbackDns)
             {
-                var dnsClient = new DnsClient(dns, forceTcp: true);
+                var dnsClient = new DnsClient(dns);
                 var address = await this.LookupAsync(dnsClient, domain, cancellationToken);
                 if (address != null)
                 {