The thermal protector is composed of a heat-conducting metal shell, a bimetal element welded with a silver alloy contact, a conductive support, an insulating fixed base, a static contact plate and a heat-resistant wire. Current through the impedance of the bimetal element, in the case of abnormal work, as the current increases or the surrounding temperature rises to the set temperature value, the bimetal element quickly action, open the contact, cut off the circuit. When the device is cooled to the safe working temperature, the contact automatically closes and returns to the normal working state.