The invention relates to a hydraulic pump pressure maintaining automatic testing device. The device comprises an electronic control system, an electrolyzed water channel system and a mechanical structure. The mechanical structure comprises a frame and an operation panel. The electrolyzed water channel system comprises a water injection system, a loading system and a pressure testing instrument. The electronic control system includes a pump motor and further includes a loading pump motor start-stop, speed regulation and protection circuit and a measurement and control system. The measurement and control system completes pressure testing of a water pressure test of a device under test, pressure maintaining data analysis and storage and automatic control of pressure maintaining time setting,timing and pressure maintaining start and stop. The measurement and control system is connected with a water injection system, a loading system and a pressure testing instrument of the electrolyzed water channel system to control the testing device to complete testing of the device leakage rate. The hydraulic pump pressure maintaining automatic testing device has the advantages of being simple inoperation and capable of being used for leakage rate testing on environment protection product testing devices like an electrolyzed water quality measurement and control assembly comprehensively in real time by using a pressure maintaining leakage testing method.