Domain name resolution method, DNS (Domain Name Server) server and system

The invention discloses a domain name resolution method, a DNS (Domain Name Server) server and a system. The method comprises the following steps of: after the DNS server receives a domain name resolution request initiated by an accessed user, a corresponding DNS response message is obtained; when the obtained DNS response message is a disconnected DNS response message based on a UDP (User Datagram Protocol), a value of a specified zone bit is set in the DNS response message to generate a DNS response message after change; after the value of the specified zone bit is set to indicate that the accessed user receives the DNS response message after change, the domain name resolution request initiated in a TCP (Terminal Control Protocol) mode is cancelled and the DNS response message after change is returned to the accessed user. By adopting the scheme, the domain name resolution search based on the TCP mode is avoided, therefore, the system can not be attacked by the TCP mode, the DDOS (Distributed Denial of Service) attack resisting capability of the system is effectively increased, and the domain name resolution efficiency of the system is improved.