A terminal box for a centrifugal switch of a motor, having at least a housing, a movable control rod extending from the housing, a cavity disposed on end surface of the housing, and a thermostat disposed in the cavity. A protruding block is disposed on the inner wall of the cavity. A reversed hook is disposed on outer side wall of the thermostat. The bottom of the protruding block abuts against the top of the reversed hook whereby fixing the thermostat in the cavity. The invention effectively simplifies the installation structure of the thermostat and the cavity; the overall installation structure is simple and stable, the cost of the structure is low, and structure of electrical connection in the terminal box is simple and reliable.