This paper presents an electromechanical, two axes sun tracking system based on single chip microcomputer (MCU). According to the path of the sun in the space, the earth coordinate system is chosen to design the tracking device. The whole device consists of one worm-drive and one gear-drive, which is operated by two step motors. The photodiodes are used as photoelectric sensors to detect the pointing of the sun. Eight photodiodes are installed in the diameter hole of the hemispherical surface. The comparative signals produced by the diodes array are performed to judge the orientation of the solar panel. The circuit of the control system based on MCU is demonstrated. The comparative signals may be amplified, A/D converted. After a series of signal processing, the signals are sent to the MCU which will produce the pulse to control the speed and steering of step motors. The sun tracking system is an efficient system for solar energy collection. It has been proved that the sun tracking systems can collect up to 50% more energy than what a fixed panel system collects.