The opening and closing time test of 500kV high voltage circuit breaker can evaluate the mechanical characteristics and three-phase synchronization performance of the circuit breaker. Due to the influence of the earth resistance circuit, the traditional test method of circuit breaker opening and closing time can not be carried out when both ends are grounded. This paper first introduces the differential coil used to collect the signal, and then according to the requirements of field test, puts forward a test method for the opening and closing time of circuit breaker under the condition of double terminal grounding, and gives the basis for judging the opening and closing signal time. Finally, it compares and analyses the results of this method with the traditional high voltage circuit breaker opening and closing time test method, and obtains the conclusion of high voltage circuit breaker. The test method of grounding time division and closing time at both ends of the circuit breaker can fully meet the needs of field maintenance, which provides a new idea for the opening and closing time test of 500kV high voltage circuit breaker.