Bridge drainage device capable of automatically adjusting drainage amount

The utility model discloses a bridge drainage device capable of automatically adjusting drainage quantity, which comprises a bridge body, two placing cavities are arranged in the bridge body, a water storage tank is arranged in the bridge body, two supporting rods are fixedly connected to the inner side wall of the water storage tank, a ball valve is arranged in a vertical pipe, and a water outlet is formed in the vertical pipe. A first touch switch is fixedly connected to the bottom of the lifting block, and a first control valve is arranged on the surface of the first drainage pipe. When the transverse groove, the vertical pipe, the lifting block, a first touch switch, a ball valve, a first drainage pipe and a third touch switch are used in a matched mode, rainwater can be filtered in advance when entering the water storage tank in rainy days, and when the water amount reaches two preset values in the water storage tank, the water storage tank can be used for storing water. The first drainage pipe and the s