Mechatronic positioning servo system is a typical nonlinear system, and also usually exist many uncertainties. The nonlinear and uncertainties make the conventional controller not yield to the required system performance. Aiming at unknown dynamic friction parameters and unknown load characteristic, a adaptive friction compensation is designed for the servo system．The design of the controller is simplified by using a dynamic filter and an adaptive robust controller is designed to improve the system steady state accuracy and the robustness respectively. The output tracking error is proved to converge to a small neighborhood around zero and the performance of system tracking error can be guaranteed by appropriately choosing design parameters and introducing an initializing technique. Simulation and experiment results are shown to effectively inhibit the disadvantageous influence of friction and lay the foundation for improvement of dynamic performance of servo system.