In this paper. a prototype of a mobile Sun tracking system is proposed. The proposed system uses 2-axis tilt sensor and 3-axis magnetic sensor to measure the orientation and the posture of the system according to the horizontal system of coordinates, which are used to compensate the slope effects. Then through astronomical calculation using the time and position information obtained by GPS sensor the azimuth and altitude of the Sun from that location is calculated. The position of the Sun is converted to that of the mobile Sun tracking system coordinates and used to control A-axis and C-axis of the system.