The invention discloses a device for removing rust of underwater pier column steel bars and repairing concrete surfaces. The device comprises a suspension bracket, a movable sleeve and a control box, wherein the suspension bracket is fixedly arranged at the top of a bridge pier, the movable sleeve is formed by splicing at least two modules with the same shape along a circumferential direction, and pressing devices and rubber strips are arranged at joints; each module comprises a body, the upper part and lower part of the body are provided with convex edges, rubber strips are also arranged at the joints of the convex edges and the bridge pier, and the left and right sides of the body are provided with connecting parts; the convex edges are provided with vent holes and drain holes relative to the inner side of the movable sleeve, and a plurality of guniting nozzles and a plurality of liquid spraying nozzles are uniformly distributed on the inner side surface, between the upper and lower convex edges, of the body; the vent holes, the drain holes, the guniting nozzles and the liquid spraying nozzles are connected with the control box by virtue of pipelines; and a drying device is also arranged in the body. The repairing device disclosed by the invention is high in degree of automation, strong in universality, capable of being reused, and capable of effectively reducing the construction cost.