Network processor is a kind of programmable processor performing network computing with special design and optimization. It can be viewed as a tight-coupled multiprocessor system due to its architecture of multiple in-chip processors, high-speed buses and other function components. The design and development of networking systems using network processors is an emerging field that offers numerous challenges and opportunities. This paper provides the design and implementation of queue management module combining buffer management and packet scheduling for QoS provision, which uses Intel?s network processor and follows the relative differentiated service model. As the key issues, system synchronization, task assignment to threads and design difficulties are discussed in the paper.