Abstract: Aiming at promptness and stability tracking of maximum wind power while variable speed constant frequency wind power generation system running under rated wind speed, with considering constraint of mechanical torque variation, a novel control strategy based on sliding mode based extremum seeking control（SM-ESC） system for optimally tracking of maximum wind power was proposed and its stability was proved through proposition. To achieve higher control quality, an adaptive adjustment method was further presented on the basic of stabilizing conditions of SM-ESC system, avoiding complicated manually parameter adjustment. The constraint of mechanical torque variation can be taken into account through deduction and analyzing process by just adding a rotor speed reference ?ref limited link in SM-ESC system and with the adaptive adjustment method to determine the corresponding limit; thus makes smooth variation of mechanical torque without swings when tracking the optimum output curve, partly reducing the mechanical fatigue extent and prolonging service life of generation system. Simulation results show the effectiveness and validity of the control strategy and adjustment method proposed.