The invention provides a dustproof protective cover capable of being mounted on a unit brake cylinder. The dustproof protective cover comprises a housing, wherein a drainage hole is arranged at the side, near the ground, of the housing. Through the arrangement of the drainage hole, the dustproof protective cover disclosed by the invention can discharge the accumulated water in the dustproof protective cover in time, and prevent the accumulated water from entering core components of the unit brake cylinder resulting in internal damage.