Abstract: A stepper motor control system was designed based on a "PC + motion control card" scheme. First, the motion control card used and the development method of the control system are introduced. Then, an application example in a horizontally stabilized platform control system is given. This system has a good human-machine interface, good control effect, and practical application value. Keywords: Stepper motor; Motion control card; PID control; Stabilized platform 0 Introduction A stepper motor is an actuator that converts electrical pulses into angular displacement. When the stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle (called "step angle") in a set direction. The angular displacement can be controlled by controlling the number of pulses, and the speed and acceleration of the motor can be controlled by controlling the pulse frequency. Due to its advantages such as no accumulation of position error and ease of open-loop control, it is widely used in digital control systems. Stepper motor control methods include: microcontroller system control, PIE control, dedicated control system control, and motion control card control. Microcontroller systems are low in cost but difficult to develop and have a long development cycle, suitable for mass production. PID control is suitable for devices with simple motion processes and fixed motion trajectories. Dedicated control systems are used in specialized industries or on specialized equipment, such as CNC lathes and CNC milling machines. Motion control cards, relying on the powerful capabilities of computers, offer greater flexibility and can be used for equipment with complex motion processes and trajectories. The system described in this article employs a "PC + motion control card" solution. Using control software developed with Visual Basic 6.0, it achieves motion control of a stepper motor and utilizes a digital PID control algorithm, achieving good control performance. For details, please click: Design of a Stepper Motor Follow-up System Based on a Motion Control Card