Abstract: The reactor coolant pump inlet and outlet differential pressure gauge was set in HPR1000 to measure the loop flow of the reactor coolant system, and the elbow flowmeter set in the second generation progressive nuclear power unit was eliminated. The change of the flow measurement means directly affects the implementation of the flow measurement tests of RCS system. By studying the operation characteristics of the main pump and the resistance characteristics of the system, a test method based on the electric power of the main pump to measure the flow of RCS system was proposed. Combined with theoretical analysis results and engineering practice experience, the test method and acceptance criteria of the reactor coolant idling flow test were given. The research shows that the main pump electric power method can measure the flow of RCS system, and the reactor coolant idling flow can be verified by the speed change of the main pump during the idling process.