Abstract: An active queue management (AQM) algorithm based on sliding mode control (SMC) theory is proposed to solve the congestion problem in transmission control protocol (TCP) networks. The algorithm is put forward on the basis of linear TCP network congestion control model. An asymptotically stable sliding surface is designed by linear matrix inequality (LMI) to compensate for the effect of uncertainty in networks. In this way the design of the sliding surface is transformed into solving the LMI. Applying an improved reaching condition to the congestion control system, the chattering is obviously decreased. The controller satisfying the reaching condition can effectively constrain the oscillation of the queue length in router. The simulation results in different scenarios demonstrate the favorable stability and robustness of the algorithm.