The utility model discloses an operating loop testing circuit for electric power protecting equipment, which comprises a testing start signal circuit, a contact output circuit and a logic processing circuit. The testing start signal circuit is used for generating low-level testing pulse signals, the contact output circuit generates isolation weak current signals for a switch circuit breaker to pass through testing action current, and the logic processing circuit judges work statuses of operation loops of the electric power protecting equipment. The operation loop testing circuit is fine in technical feasibility and low in cost and totally adopts complex circuits and complex devices, and users can complete everyday routine inspection by means of pressing a testing button, thereby avoiding severe accidents and increasing reliability of a power supply system.