The utility model discloses a beam -ends percolating water extraction device of expansion joint department, water drainage tank that embedding slot steel, stagnant water type rubber tape, drain pipe or punchhole and pier stud side surface were established, the embedding slot steel adopts C shape section, and the mouth is pre -buried outwards to be located both sides case beam -ends portion and to lean on down in concrete box beam expansion joint department, follows case roof beam cantilever to bottom of the case equipartition to set the shape that both sides are longitudinal gradient to, embedding slot steel both ends are located the both sides rainwater collecting groove department of concrete box beam up end, the stagnant water type rubber tape of establishing the cavity with the middle part is clogged in the channel -section steel of both sides case roof beam respectively and is built in, and its both ends are located embedding slot steel both ends department, rubber tape department in mound top nadir position establishes drain pipe or punchhole, flow into the water drainage tank that dun ding preset with percolating water in, establish water drainage tank at the pier stud side surface simultaneously and push up water drainage tank with the mound and be connected, flow into at last in the ground rainwater system at the bottom of the bridge. The utility model discloses solution expansion joint department that can be fine leaks to loose and flows a great deal of technical problem and the technical problem such as change and maintenance difficulty that cause.