According to the piezoelectric effect of piezoelectric material, a vane-type wind power generator capable of automatic windward was designed by using the piezoelectric plates to convert the wind power into the electric energy. The mathematical model of the device was established. Based on the moment analysis, the parameter relation to satisfy the requirement of automatic wind was derived. The device took advantage of the wind-force to drive the piezoelectric plates vibrate and the energies generated from the piezoelectric plates were collected by the energy harvesting circuit and supplied for the load. The analysis of the moment and the investigation on the stability of the whole device show that the device can run stably into the wind under any wind direction, and it can meet the power supply requirements of small power loads such as street lamps.