The present invention discloses a method for providing QoS guarantee by an edge router, the edge router transporting user traffic between the access network and core network, the method comprising: creating a service traffic flow classification table; establishing a plurality of label switching paths; configuring the attributes of the label switching paths; classifying and conditioning the service traffic flows entering into the core network at a downlink interface of an edge router according to the service traffic flow classification table; forwarding the processed traffic by an uplink interface of the edge router according to the attributes of the label switching paths. The present invention also discloses an apparatus for providing QoS guarantee by an edge router. Using the present invention, an edge router can provide exact QoS guarantee and QoS routing control for the application flows.