A method for obtaining an address of a session initiation protocol, SIP, local survivable registration server of a branch office, comprising: receiving, by a branch device of the branch office, a domain name system, DNS, resource record for specifying the location of service, SRV, query request sent by a branch terminal of the branch office during the branch terminal startup; forwarding, by the branch device, the DNS SRV query request to a DNS server, wherein the branch device is a SIP local survivable registration server of the branch office and a DNS proxy; receiving, by the branch device, a DNS SRV response message returned by the DNS server in response to the DNS SRV query request, wherein the DNS SRV response message comprises an IP address of a SIP registration server of a central site to which the branch device belongs; adding, by the branch device, information of the SIP local survivable registration server to the DNS SRV response message, wherein the information of the SIP local survivable registration server comprises a domain name of the SIP local survivable registration server, and the domain name of the SIP local survivable resistration server is carried in Answer part of the DNS SRV response message; returning, by the branch device, the DNS SRV response message to which the information of the SIP local survivable registration server is added to the branch terminal; receiving, by the branch device, an A query message sent by the branch terminal, wherein the A query message comprises the domain name of the SIP local survivable registration server; and obtaining, by the branch device, an Internet Protocol, IP, address of the SIP local survivable registration server According to the domain name of the SIP local survivable registration server, and returning the IP address, of the SIP local survivable registration server to the branch terminal, so that the branch terminal obtains a registration service through the SIP local survivable registration server when communication between the branch office and the central site fails. receiving, by a branch device of the branch office, a domain name system, DNS, resource record for specifying the location of service, SRV, query request sent by a branch terminal of the branch office during the branch terminal startup; forwarding, by the branch device, the DNS SRV query request to a DNS server, wherein the branch device is a SIP local survivable registration server of the branch office and a DNS proxy; receiving, by the branch device, a DNS SRV response message returned by the DNS server in response to the DNS SRV query request, wherein the DNS SRV response message comprises an IP address of a SIP registration server of a central site to which the branch device belongs; adding, by the branch device, information of the SIP local survivable registration server to the DNS SRV response message, wherein the information of the SIP local survivable registration server comprises a domain name of the SIP local survivable registration server, and the domain name of the SIP local survivable resistration server is carried in Answer part of the DNS SRV response message; returning, by the branch device, the DNS SRV response message to which the information of the SIP local survivable registration server is added to the branch terminal; receiving, by the branch device, an A query message sent by the branch terminal, wherein the A query message comprises the domain name of the SIP local survivable registration server; and obtaining, by the branch device, an Internet Protocol, IP, address of the SIP local survivable registration server According to the domain name of the SIP local survivable registration server, and returning the IP address, of the SIP local survivable registration server to the branch terminal, so that the branch terminal obtains a registration service through the SIP local survivable registration server when communication between the branch office and the central site fails.