A brake cylinder dust cover is installed on a waterproof brake cylinder. The brake cylinder includes a brake cylinder body and a front cover. A waterproof dust cover assembly is arranged on the front cover. The waterproof dust cover assembly includes a dust cover fixedly connected to the front cover, and a filter felt support and a filter felt pad which are arranged in the dust cover. The filter felt support is connected with the dust cover, and the filter felt pad is fixed on the filter felt support. An outwards extending skirt is arranged at the edge of the dust cover in the axial direction thereof.