Nuclear power plant emergency power source power supply test method and system

The invention discloses a nuclear power plant emergency power source power supply test method and system, the method is as follows: making a circuit system in the pressure relief state; opening a voltage stabilizer evacuation valve; providing main pump shaft seal water; dismantling a cut-off valve element from a material replacing water tank to a high-pressure safety injection pump inlet; presetting low pressure safety injection pump outlet valve opening degree; in the reactor pressure vessel covered condition, triggering a safety injection signal; starting a low pressure safety injection pump to pressurize a high-pressure safety injection pump to take water from the material replacing water tank to injecting water into a circuit; and due to the dismantling of the cut-off valve element from the material replacing water tank to a high-pressure safety injection pump inlet, flowing water from the low pressure safety injection pump outlet back to a low pressure safety injection pump inlet to form large flow circulation to star an emergency power source power supply test under full load conditions. The beneficial effects are that: the method can be performed without the reactor pressure vessel cover opening condition, and is not limited by test execution windows, other debugging work may not be restricted during the test period, and the debugging working period can be saved.