A power uninterruptible relay protection tester of the present invention comprises a power supply system and a test system, the power supply system comprises an energy storage circuit, a conversion circuit and a power supply output circuit, and the test system comprises a main circuit and a test circuit. The energy storage circuit is connected with the commercial power, the conversion circuit and the power supply output circuit, the main circuit is connected with the power supply output circuit, the test circuit is connected with the power supply output circuit via a voltage transformation rectifier unit, and a power amplification unit of the test circuit is connected with a relay. When the commercial power is inputted, the energy storage circuit stores the electric energy, and the commercial power supplies power to the power supply output circuit via the conversion circuit; when the commercial power is not inputted, the energy storage circuit discharges and supplies power to the power supply output circuit via the conversion circuit. The power supply system of the present invention has an energy storage function, and supplies power to the relay protection tester on the condition that the commercial power fluctuation is large, the power supply quality is poor, or the commercial power is interrupted, thereby not influencing the precision, and providing the quality qualified test data.