The invention discloses special channel steel three-dimensional surface derusting equipment for a bridge. The equipment comprises a worktable, support legs, a water spraying pipe, a guide drum, a water tank, a derusting roller, a derusting block and a handle; the left end of the upper surface of the worktable is fixedly connected with the water spraying pipe; a left bracket is arranged on the right side of the water spraying pipe; the side wall of the left bracket is fixedly connected with a first motor; a groove is formed in the upper surface of the worktable; a two-way lead screw is arranged in the groove; slide blocks respectively sleeve two ends of the two-way lead screw; a right bracket is arranged at the right end of the worktable; the upper surface of the right bracket is fixedly connected with a fourth motor; fixed plates are respectively arranged on two sides of the fourth motor; a slide frame is arranged between the fixed plates; the derusting roller is used for derusting the lower surface of channel steel; and the derusting block continuously moves left and right in the groove of the channel steel to derust the inner wall of the groove of the channel steel. The equipment can derust the side surface and the bottom surface of the channel steel and the inner wall of the groove at the same time, so that the workload of workers is greatly reduced, and the derusting efficiency is improved.