The invention discloses a cleaning device used for a cooling water system in a converter valve. The device comprises a cleaning box (1), water pumps (2), a nitrogen cylinder (5), a stirrer (13) and a heater (14), wherein the number of the water pumps (2) is at least two, and the water pumps are respectively connected with a check valve (3). The two check valves (3) are connected with a recirculating valve (7), a first pressure meter (4), a relief valve (6), a first valve (8) and a second valve (9) in parallel. The other end of the recirculating valve (7) is inserted into the cleaning box (1); the other end of the first valve (8) is connected with a fourth valve (11) in series; the other end of the second valve (9) is connected with a third valve (10) in series. The device can clean the cooling water system in the super/extra high voltage converter valve regularly on the premise that safe operation is not affected, and has the advantages that gas-water-combined cleaning and pulse cleaning can be performed, cleaning conditions can be controlled conveniently, and the device is safe and easy to operate, good in effect and low in cost.