Abstract: An adaptive fuzzy sliding mode control scheme was proposed for the position tracking control of chain driving mechanical servo system in presence with meshing impact, parameter perturbations and nonlinear friction. Comparing with traditional adaptive sliding mode control, the adaptive scheme was adopted in this paper to estimate the time-varying system parameters instead estimating the upper bound of the model uncertainty, and the influence of model uncertainty was effectively reduced. And then a fuzzy logic system was designed to remove the discontinuous control term in the traditional sliding mode control, and the chattering in the control effort was reduced. Actual velocity was replaced by desired velocity in the nonlinear friction compensation, thus the influence of measurement noise was reduced, and the control performance was improved. Experimental results show that the proposed scheme is insensitive to parameter variations and external disturbance, and the control precision is high.