In order to avoid interference to railway operation, the common construction methods for existing railway Bridges over the span include turning and pushing. The turning method takes a short time and there is no system conversion in the construction process, so it should be the first choice when conditions are not limited. When the bridge location is unable to turn due to the influence of existing buildings, the jacking method can be considered. Considering the need for later maintenance and maintenance, it is generally not appropriate to use steel structures to cross existing lines. In the design of prestressed concrete beams constructed by push-up method, it is necessary to consider the temporary beam arrangement, the connection between guide beam and concrete beam, the stiffness of permanent pier and temporary pier, and the reasonable line shape of beam bottom. It is easy to have such problems as excessive push force, deformation of slide, unplugging of slide block, excessive displacement of pier top, cracking of pier bottom and cracking of beam body at the joint of guide beam and concrete.