Abstract: According to the special requirements of micro-part resistance spot welding technics, a transistor-style high-frequency power supply was designed, which could improve the control precision of the power. The main circuit structure, the working principle, and the controlling core dsPIC30F6010 were introduced. The 100 kHz frequeney was applied for the first time in the resistance spot-welding power supply field, as a result, the control accuracy and response speed were greatly increased, and the welding current waveform were excellent. It is proved that this power supply has a unique advantage in precise welding and is more adaptive, compared with other micro-part welding powers supply.