The invention provides a method and a system for classifying service flow. The method comprises the following steps: configuring corresponding relationship between service types and service interfaces; receiving user flow accessed to a circuit by a user, and matching the user flow with the matched service types; transmitting the user flow to the service interfaces corresponding to the service types according to the corresponding relationship between the service types and the service interfaces; configuring the service interfaces into virtual interfaces and interface inner rings binding the virtual private network attribute to ensure that the service flow is endowed with the virtual private network attribute; and searching a virtual private network route and forwarding the service flow by the virtual private network. The invention pre-maps the service types and a bearing channel of services and stores the mapped service types and the bearing channel into a service member corresponding relationship table and forwards according to the relationship table, thereby realizing the quick forwarding of the flow.