In order to meet the requirements of automatic inspection equipment in non-destructive testing (NDT) of nuclear power plant, a universal, low-cost, small DC motor motion controller based on STM32 is developed. The controller is mainly composed of micro control unit (MCU) minimum system, motor driving circuit, signal processing circuit of encoder and communication circuit. The duty cycle of pulse width modulation (PWM) is adjusted by incremental PID algorithm and integral separation position PID algorithm in STM32, achieving the ideal effect of rapidity, stability and small steady-state error. Based on this controller, a two-axis motion control system is developed to realize the application of automatic raster scan for the weld joint region of the pipeline outer wall.