A method and system for implementing data routing of a roaming user are disclosed. The method comprises: configuring a roaming protocol between the home network and the roaming network; during the registering process of the user in the roaming network, performing an interactive negotiation between the home network and the roaming network, so as to determine one of the home network and the roaming network to allocate IP address according to the roaming protocol between the home network and the roaming network; and establishing the IP access bearer based on the IP address.