The invention discloses a waterproof brake cylinder. The waterproof brake cylinder comprises a brake cylinder body and a front cover, wherein a waterproof dustproof cover assembly is arranged on the front cover and comprises a dustproof cover, a dust filtering felt frame and a dust filtering felt cushion, the dustproof cover is fixedly connected to the front cover, the dust filtering felt frame and the dust filtering felt cushion are arranged in the dustproof cover, the dust filtering felt frame is connected with the dustproof cover, and the dust filtering felt cushion is fixed at the dust filtering felt frame; and skirt extending outwards is arranged at the edge of the dustproof cover along the axial direction of the dustproof cover. According to the waterproof brake cylinder, by arranging a sealing structure at an easy-inflowing position of an existing brake cylinder, the suction of rainwater into the cylinder body through a negative pressure generated in the brake cylinder during the relieving of the brake cylinder can be effectively prevented, and a waterproof effect is achieved, so that the service life of the brake cylinder is prolonged, and the traffic safety is guaranteed.