Abstract: Based on the day-ahead forecast of system load and wind power output,this paper focuses on the optimization of the daily joint operation of wind power and pumped-storage plants,and a new mode of joint operation is proposed.A mixed-integer programming formulation is built to maximize the daily profit of the wind farm and the pumped-storage plant,where the time interval is 15 minutes and the constraints of unit startup-shutdown times are considered.The state change of units is taken into consideration by a quadratic constraint.The whole formulation is solved by commercial optimization software under MATLAB environment.A test case is developed based on the parameters of a practical pumped-storage plant.Simulation results indicate that the coordinated operation of wind farm and pumped-storage plant greatly reduces the negative impact of random wind power output on the power system operation and achieve significant economic and social benefits.