The invention provides a water drainage device for a wet-type electric precipitation device. According to the technical scheme, the water drainage device comprises a blow-off pipe communicated with the lower end of a dust hopper of the electric precipitation device. At least two water outlet pipes are arranged on one side of the blow-off pipe, the blow-off pipe is communicated with each water outlet pipe through an overflow pipe, water inlets of all the overflow pipes are formed in the portions, at different heights, of the blow-off pipe, and the height of the water inlets of the overflow pipes is smaller than the height of overflow openings. The height of the overflow opening of the overflow pipe at the uppermost end is smaller than the height of a cathode frame of the electric precipitation device, a blow-down valve is arranged on the portion, on the lower portion of the water inlet of the overflow pipe at the lowermost end, of the blow-off pipe, and overflow valves are arranged on the overflow pipes. According to the scheme, the blow-off pipe is communicated with the at least two upward-inclined overflow pipes from bottom to top, if the overflow pipe at the lower portion is blocked, the overflow pipe above the blocked overflow pipe can still play the overflow role, and thus the safe operation of the electric precipitation device is ensured.