A high-precise automatic positioning system for data sample of linear time grating sensor is designed. In order to achieve linear time grating sensor of data sample, improve measure work efficiency, an ARM MCU is used as a major chip to control the stepper motor to rotate. In this way, the stepper motor drives the ball screw, the moving probe of linear time grating sensor and reading head of linear grating to move synchronously. A high-precision automatic positioning of the system hardware is designed. In addition, ARM controlling circuits and stepper motor driving circuits are designed. Therefore, the special communication interface is designed for the high-precision automatic positioning system, receiving the feedback signal from time grating sensor, forming a high-precision closed loop control system, and communicating with upper computer by serial. Experiment results prove that the positioning precision of control system can reach 0.1 um.