Abstract: This paper proposes the synchronous control method of servo motor driving ball-screw for a "U" shape pitching door-frame movement mechanism with low rigidity,big inertia and high synchronization demand.Using PLC positioning function module FM353,digital-frequency cascade master-slave control mode provided by servo driver,and high precision calibration compensation method of artificial interpose for nonsynchronous motion of door-frame mechanism,the movement of door-frame mechanism achieves the synchronous precision requirement of 0.1 degree.