The experimental teaching platform for direct current (DC) motor speed-regulating system is based on the main C8051F040 micro-controller (MCU), and the double closedloop reversible pulse width modulation (PWM) DC speedregulating full digital system is designed. The method of 16bit PWM digital pulse wave was proposed by a programmable counter array output of using C8051 MCU to replace the digital pulse trigger. Current sampling, speed detection, analog-digital conversion (ADC), PWM signal generation, and the motor driver circuit were designed. The methods of engineering design were used to design current regulator and speed regulator of proportion integral (PI) parameters, which were validated by MATLAB and implemented by software programming. The speed value, the current and PI parameters could be input and modified by keyboard online function of the system, the direction of motor rotation could be judged, the speed, and the current and temperature values of power modules could be displayed, with faults alarm functions. The actual operation of experimental teaching platform is reliable, which can meet the requirements of experimental teaching.