QoS realization method in transitional environment and PE router

The invention discloses a QoS realization method in the transitional environment and a PE router, relating to the technical field of the router in communication network. The method in the invention comprises the following steps: adding a field dedicated to QoS mapping at a data packet header after the data packet is received by a first PE router and after connection is established between the PE routers; modifying the content of the newly-added field to be the preset value according to the QoS strategy and a flow label in the data packet header, wherein, the preset value is corresponding to one or a plurality of QoS processing; transmitting the modified data packet by the first PE router; carrying out corresponding QoS processing on the data packet which contains the field dedicated to the QoS mapping according to the content of the field by a second PE router after the second PE router receives the data packet transmitted from the first PE router. The technique in the technical scheme of the invention is simple and feasible, and is flexible and convenient to manage for carriers.