Abstract: Designs a point light source tracking system based on TI Company′s MCU MSP430F149. The system is composed of four parts：white LED driver circuit，light source detecting circuit，data processing and tracking control device. The MCU processes the data of light intensity which detected with photosensitive resistances device，and two stepper motors moving in X/Y direction with PWM method，so as to make the laser pen track the light source. Introduces the working principle of the system，gives the hardware design circuit and part of mechanical structure，and elaborates the key tracking algorithm. The experiment results show that this system can track the light source better and has self-adaptability；it has good reference value in the tracking of solar energy.

Key words: MSP430F149, point light source tracking, photosensitive resistance, stepper motor