Provided are a method and device for processing an IPv6 address, DHCPv6 relay equipment and a DHCPv6 server. The method includes that: an IPv4 information option, of which an address field is an IPv4 address, in information options of an IPv6 message is monitored; an IPv6 prefix corresponding to the IPv4 information option is acquired; and an IPv6 address is synthesized according to the IPv4 address in the IPv4 information option and the IPv6 prefix. Through the present disclosure, various problems appearing when a server is still deployed in an IPv4 network in an IPv6/IPv4 network interworking process and the problem of complexity in network maintenance in the related art are solved, and the effects of automatically synthesizing the IPv6 address by virtue of network equipment, reducing complexity in system maintenance and enhancing convenience for transition from IPv4 to IPv6 are further achieved.