Taking the Yongjiang Bridge reinforcement project of Nanning City as an example, the external prestress reinforcement measures were adopted and the finite element analysis program midas was used to analyze the external prestress reinforcement design. The results of calculation and engineering practice show that the external prestressing reinforcement method can effectively improve the internal force and stress distribution of the original structure, and increase the bearing capacity of each control section of the structure, especially the downwarping deformation of the free end of the beam. Therefore, it can be used as an important reference for the design and construction of similar external prestressed reinforced Bridges.