Abstract: This paper introduces the basic functions of the ATmega128 microcontroller and designs a permanent magnet brushless DC motor control system based on it. Taking full advantage of its fast processing speed and rich on-chip peripherals, the PWM method is adopted to realize the position and speed control of the brushless DC motor. The overall design scheme and corresponding software strategy are also presented. Keywords: Brushless DC motor; ATmega128 microcontroller; PWM control 1 Introduction Traditional brushless DC motor control systems are generally composed of discrete analog devices. Analog control systems are convenient to use, inexpensive, and widely used. However, analog devices also have inherent drawbacks: component characteristic parameters are affected by temperature; devices age; maintenance is inconvenient, and upgrades are impossible. With the continuous improvement of microprocessor performance, digital control systems based on microprocessors are gradually being applied to the control of brushless DC motors and have achieved very good results. It will eventually replace analog control systems. The ATmega128 microcontroller is a high-performance, low-power CMOS microprocessor with enhanced built-in Flash and a reduced instruction set CPU (RISC). It integrates a wealth of peripherals, greatly simplifying the hardware circuitry of the control system, improving system performance, and meeting the requirements of motor control systems. This article discusses the ATmega128 microcontroller control system for brushless DC motors and the control strategy for brushless DC motors. For details, please click to download: Brushless DC Motor Control System Based on a New Microcontroller.