Internet real-time multimedia communication brings a further challenge to Quality of Service (QoS). A higher QoS in communication is required increasingly. As a new framework for providing QoS services, Differentiated Services (DiffServ) is undergoing a speedily standardization process at the IETF. DiffServ not only can offer classified level of services, but also can provide guaranteed QoS in a certain extent. In order to provide QoS, DiffServ must be properly configured. The traditional DiffServ mechanism provides classifier for edge router to mark the different traffic streams, and then the core router uses different Drop Packet Mechanisms to drop packets or transmit data packets according to these classified markers. When multiple edge routers or other core routers transmit data packets high speedily to a single core router, the core router will emerge bottleneck bandwidth. The most valid solution to this problem is that the edge router adopts drop packet mechanism. This paper proposes an Modified Edge Router Mechanism that let the edge router achieve marking, dropping and transmitting packets of hybrid traffic streams based on DiffServ in a given bandwidth, the core router will only transmits packets but won’t drop packets. By the simulation of ns2, the modified mechanism ensure the QoS of high priority traffics and simplify the core router, it is a valid method to solve the congestion of the core router.