In this paper, according to the control requirements of the claw pole motor with PM outer rotor, a sensorless motor controller was designed based on ML4425 and PIC16F877A. Based on Matlab/Simulink, mathematical model and control system model of the motor were established. A pure hardware motor controller was designed. The controller includes a regulated power supply, ML4425 external circuit, PIC16F877A external circuit, three-phase power bridge and drive circuit, smooth start-stop circuit, speed control circuit, speed display circuit. Experimental studies were carried out using the controller. Experiment results the control system works well.