The DC motor speed control system based on single-chip microcontroller is designed in this project. It utilizes PWM signals to control the speed of the DC motor. The preset speed is converted into a certain duty cycle pulse signal by the single-chip microcontroller and output to the DC motor drive module. An optical rotary encoder aligned with the DC motor collects pulse signals, which are then input to the single-chip microcontroller for analysis to obtain the real-time motor speed. The difference between the real-time speed and the preset speed is calculated, and converted into a certain duty cycle to adjust the pulse output to the DC motor drive module. This process is repeated continuously to maintain the desired speed. The system adopts the STC 89C52RC single-chip microcontroller as the main control chip, L298N chip as the DC motor driver, and LCD1602 liquid crystal display screen for real-time speed display. The hardware circuit design of the system is reliable, with strong anti-interference ability, fast speed adjustment, and a fluctuation range of 1%. Keywords: Single-chip Microcontroller, Motor Drive, LCD Display, Speed Setting.