TH-AID type thermo protector is composed of the parts of thermal conductive casing, bimetallic parts welded with silver alloy contact point, conductive bracket, insulation fixation stand, fixed contact strip and heat resistance cable. When current passes through the bimetallic parts with resistance and in case of abnormal operation, along with the increase of current or the environment temperature rises to the set value, the bimetallic parts perform quick action, opens the contact point, and disconnects the circuit. When the device is cooled to the temperature for safe operation, the contact point will automatically closes and recover normal operation.