Disclosed is a method for updating DNS of host in IPv6 stateless address auto-configuration, wherein an option is added in the RS message sent by a host and/or RA message sent by a router, said option including information for negotiation of updating DNS of host. Based on said information, the host negotiates with the router to determine whether the host or the router register, the mapping between the global address of the host and the full domain name of the host, to a DNS server, to complete updating the DNS of the host. This invention enables the host to correctly identify the matching relation between domain name suffix information and address prefix, and achieves the negotiation of updating DNS domain name between the host and the router. Since DNS updating is performed by a router instead of the host, the DNS updating would become simple and safe.