Abstract: In order to investigate the effect of strengthening with U-shaped plate and secondary corrosion on the mechanical properties of corroded RC beam, 7 pieces of test beams were designed to analyze the strain law, deformation characteristics, failure mechanism, et al. By using the ABAQUS finite element software, numerical simulation was carried out to study the influence of thickness and strengthening position of U-shaped plate on the performance of the strengthened beam. The results show that strain distribution of the mid-span for the test beams satisfies the plane-section assumption. The height of the neutral axis is roughly in line with the law:the height of neutral axis of the corroded beams and the corroded-strengthened-corroded beams is higher than that of the corroded reinforced beams. When the load increases to a certain extent, the anchoring effect of the U-shaped plate starts to work. In the middle and late stage of loading, the shear force shared by the three U-shaped plates on the same side is uneven, and the uneven corrosion leads to the different strain growth of U-shaped plate at both ends. The cracks of both strengthened beams and those with secondary corrosion appear more sparsely, which tend to locate in the middle span region, while the inclined cracks gradually become less obvious. The cracking load and the ultimate load of beams strengthened with U-shaped plates are improved, and the plastic characteristics are more obvious, which mainly exhibit bending-shear failure. The secondary corrosion and inhomogeneity change the deformation of components, which affects the failure mode. Compared with experimental results, the error of the ultimate load, the deflection of the ultimate load and the energy absorption value of numerical simulation results were in the range of 4.22%, 9.7% and 9.9%, respectively. It is more suitable to improve the bearing capacity by adopting a reinforcement thickness of 3 mm, and the strength and rigidity of the structure can be improved by arranging the U-shaped plate at the beam ends.