Abstract: In order to achieve beam scanning of mechanical phased array antenna, the stepper motor is adopted to drive a helical antenna element to rotate to a predetermined radiation phase. In order to optimize the open-loop control strategy of stepper, and improve the control speed and accuracy, the influence of running curve on the stepper motor control performance was studied. According to operating principle of stepper motor control system, a simulation model of stepper motor open-loop control system was constituted based on Simulink, and on this basis, the two trapezoidal and parabolic running curves were simulated. The simulation results show that, the control of running curve to the stepper motor was achieved accurately in the simulation model. Using trapezoidal running curve in the control cycle of 100 ms, the maximum rotation angle of the stepper motor can reach 270. Using parabolic running curve, the maximum rotation angle of the stepper motor can reach 360. Parabolic running curve has better control velocity in open-loop control system.