A metal oxide varistor integrally formed with a heat protection structure that will automatically go to open circuit in conditions of overheating due to sustained over-voltages. The metal oxide varistor integrally formed with a heat protection structure has a body, an insulation bracket, a number of terminals and a fuse. The insulation bracket is deposited on the body and has a number of slots. The fuse connects to the body and one of the terminals. The fuse is mounted one of the slots of the insulation bracket. The fuse reacts to the overheating timely and the melting fuse spreads quickly with the assistance of capillary action evolved by the slots of the insulation bracket to speed up the action to go to open circuit in against damage due to sustained over-voltages.