In view of the torus worm tester system control and positioning accuracy, the Cortex  M4 as the main controller, the control stepper motor to drive the objective table movement, stepper motor adopts closed loop control. the grating ruler for realtime detection of XYZ guide information, the grating signal as the feedback signal, constitute a closedloop motion control system, realize coordinate system XYZ axis movement and high precision positioning of the turntable rotation. Stepper motor driver uses hardware and software subdivision method, overcome the stepper motor step crawl and lost phenomenon. Experiments show that the system adopts the closed loop control, step motor subdivision method of software and hardware, and realizes the three axes of ±2 μm precision positioning, to ensure the torus worm tester accurate measurement.