Embodiments of the present invention provide an address allocating method, including: configuring both a DNS server and a DNS64 server for one access point of a gateway; determining whether a terminal requesting access to a network server supports the IPv4 protocol stack; and if the terminal supports the IPv4 protocol stack, allocating the terminal a DNS address directing to the DNS server; where, the DNS server is configured to send an IPv4 address and/or an IPv6 address of the network server to the terminal, and the DNS64 server is configured to synthesize an IPv4 address of an IPv4 network server supporting the IPv4 protocol stack only into an IPv6 address and send the IPv6 address to the terminal. The embodiments of the present invention also disclose an address allocating apparatus and system. With the present invention, various defects of an NAT64 are avoided.