In this paper a fuzzy proportional-Integral (FPI) controller is designed as an Active Queue Management (AQM) in internet routers to improve the performance of PI controller for congestion avoidance in computer networks. Firstly the parameters of FPI controller are selected by trial and error method, but to get the best controller parameters the Genetic Algorithm (GA) is used as an optimization method for tuning the FPI parameters. The analytical results for linearized TCP/AQM model are presented in MATLAB version 7.0. From the obtained results, a faster response time as well as the regulation of the output to a constant value by the designed FPI controller is clearly observed and it is noted that the FPI controller provides good tracking performance under different circumstances for congestion avoidance in computer networks.