The invention discloses a main circulating pump shaft-seal water leakage detection method and device of a water-cooling system of a high voltage direct current converter valve. The device comprises a water collection groove, a water storage device and a detection alarm device, wherein the water collection groove is connected with the water storage device by a honeycomb duct, the detection alarm device is connected with a controller by a periphery circuit, the controller is connected with a memory, an amplification circuit and a wireless transceiver, the detection alarm device comprises a first detection alarm device, a second detection alarm device, a third detection alarm device and a fourth detection alarm device, the four alarm devices are arranged on the inner wall of the water storage device from the bottom to the top of the water storage device, a cover is arranged on the funnel-shaped water collection groove, a seal cover and a drainage valve are arranged on the water storage device, and the honeycomb duct is a plastic hose with a diameter of 0.8 CM. The device comprises a plurality of detection alarm devices to perform asynchronous detection, the detection information is clearer, and the device has the urgent and slow alarm function and is convenient to operate by operators.