The invention discloses a thermal relay which relates to the technical field of electric protection equipment manufacture. The thermal relay comprises an insulating housing. The insulating housing is internally provided with a normally closed static contact, a normally open static contact and a moving contact which is arranged at one end of a push rod. The moving contact is movably connected with the normally closed static contact and the normally open static contact respectively for switching off and switching on a circuit. A heating element winds the outer surface of shape memory alloy with double memory effects. When overload of a motor occurs, large current causes the heating element to generate heat. The heat makes the shape memory alloy bend, thereby pushing a guiding board to move. The guiding board further pushes the push rod, so that the moving contact is separated from the normally open static contact, thereby switching off the circuit, stopping the power supply to the motor and protecting the motor. The thermal relay can settle a problem of no enough reaction sensitivity of the thermal relay when motor overload occurs.