A highperformance analog drive system for DC brushless motor with complex programmable logic device (CPLD) as core was described. Full hardware circuit design, trapezoidal commutation and PWM speed control strategies were adopted, so it had higher response characteristics.For the analog drive system,the commutation torque ripple of the motor under four PWM modulation methods were derived and calculated. An improved PWM speed control strategy was proposed, namely the system was controlled by switching different PWM modulation modes according to different duty cycles.The torque ripple values of the motor which was controlled by improved PWM speed control strategy and the traditional PWM speed control strategy were compared. An experimental platform was built, and the commutation torque ripple of the motor with the improved PWM speed control strategy under different duty cycles conditions was tested. The correctness of the improved PWM speed control strategy was verified.