Underwater vehicle requires small volume, stable motion, low power consumption, reliable performance, and easy operation. In this study, the motion control system of underwater vehicle is built with STM32F407 as the main control unit, and the software structure and data acquisition flow are designed. The data test of the thruster is carried out, and the ROV space motion coordinate system is established. The equations of motion of the vertical plane are obtained and the simulation analysis of the angle and depth of the vertical plane under the step response is carried out. The stability and reliability of the motion control system are further verified.