A method and a system for implementing an ID-Locator (ID/LOC) mapping are disclosed. The method includes: after allocating a new IP address to User Equipment (UE), the network side sending an ID/LOC mapping request to an ID-LOC-split Mapping Functional Entity (ILM-FE); and the ILM-FE returning a response with mapping information to the network side according to the received ID/LOC mapping request. The method initiates the ID/LOC mapping based on a network in an ID/locator separation in NGN (IPSPLIT) network, which improves the efficiency of the ID/LOC mapping.