Active queue management (AQM) is a very active research area in networking. As a complementary mechanism to the congestion control of end-to-end systems, AQM, used on the intermediate nodes, can provide high throughputs for routers and control the queue length effectively at the same time. Based on a model of TCP and AQM, a new PID controller is designed analytically using H∞ optimal control theory in this paper. The specialty of this controller is that a single parameter tuning method is proposed, through which the nominal performance and robust performance can be adjusted monotonically to achieve the trade-off. The performance of the controller is verified and compared with other methods using NS simulations. The result shows the advantages of the proposed PID controller.