Rainwater drainage device for building construction

The utility model discloses a rainwater drainage device for building construction, which comprises a filter box arranged at the front position of the bottom of a drainage tank, a filter mechanism is arranged in the filter box and comprises a cover plate, a water inlet matched with the cover plate is arranged at the top end of the filter box, and a water outlet matched with the cover plate is arranged at the bottom end of the filter box. The cover plate is movably mounted in the water inlet, mounting frames are fixedly connected to the positions, close to the front end and the rear end, of the bottom end of the cover plate, a plurality of winding rollers are rotatably mounted on the inner sides of the two mounting frames, a filter plate is arranged in the filter box and located below the winding rollers, and a first drainage pipe is connected to the bottom end of the filter box in a penetrating mode; the end, away from the filter box, of the first drainage pipe is connected with a second drainage pipe through