Abstract: Following the model of proportional differentiated services, a queuing management algorithm is presented, which is fit for network processors. This algorithm contains two parts, the one using for loss ratio control while packets come into the queue called RR-PLR (round-robin based proportional loss rate); and the one using for delay control while packets go out of the queue called WRR-PAD (WRR based proportional average delay). To avoid division and sort operation, this algorithm uses the round-robin mechanism. Its complexity is O(1) and it's very fit for the architecture of network processors. The simulation in NS2 shows that this algorithm can achieve the proportional differentiated service in both average packets loss ratio and average queuing delay. A prototype of the algorithm has also been implemented in the Intel IXP2400 platform. The test result shows that the whole system can reach 1.125Gbps (64 bytes per packet, i.e. 2.25Mpps) and achieve the proportional differentiated service at the same time.