The utility model relates to a disc brake, which belongs to the braking devices and can be applied to a winding engine. The disc brake is unclamped by hydraulic pressure and braked by spring force. The utility model comprises a casing which is connected with a regulating nut, a brake-releasing oil cylinder is arranged in the casing and the regulating nut, the inner part of a cavity of the brake-releasing oil cylinder is provided with a piston which is concentric with the cavity, a sealing ring is arranged between the brake-releasing oil cylinder and the piston, an oil inlet in which an oil input duct is arranged on the brake-releasing oil cylinder, and the inner part of a cavity which is formed by a cylindrical body and the brake-releasing oil cylinder is provided with springs. The side of the cylindrical body, which backs on to the brake-releasing oil cylinder, is connected to a brake block and a circular disk is arranged outside of the piston. The circular disk, the piston and the cylindrical body are connected by a plurality of connecting pieces which are arranged at the circumferentail side of the circular disk. The spring force brake of the utility model has the advantages of simple structure, good sealing effect, easy operation and convenient maintenance and solves the technical problem that the service performance of a brake is influenced by the accuracy of fabrication and installation in the prior art.