A solar tracker with intelligent switching ability of working modes is constructed to improve its performance and reliability under several weather conditions.How to choose a proper work mode of the solar tracker is investigated, and the switching method of working mode for the solar tracker is also proposed. The solar tracker has two working modes, open loop mode and closed loop one, and it consists of an imaging unit, a turntable, steppers, the subsystem of micro control unit, a computer and so on. A visual servo scheme is employed for the closed loop mode, while astronomy theory is used for the open loop mode. Moreover, the sun position in the sky is obtained by astronomic algorithms in the case of open loop. The system captures the sky image through an imaging unit, and analyzes weather conditions and external environments through image processing. In experiments, the average tracking error is 0.186 5° for the zenith angle and 0.167 9° for the azimuth angle. The solar tracking experiments indicate that the solar tracker operates reliably, and is able to work under complex weather conditions.