e static load carrying capacity of a noncorroded reinforced concrete (RC) simply supported beam is numerically simulated by ABAQUS software, and the reliability of the finite element model is verified by comparing with the test results. Based on the above model, the macroscopic mechanical properties of the beam under different degrees of corrosion are calculated. In the calculation, the degradation of the bond-slip performance and mechanical properties of corroded rebars and the coupling effect on the bearing capacity and ductility degradation of the beams are considered. e results show that, under conditions of slight corrosion, the degradation of bond-slip performance between the rebar and concrete has no significant influence on the bearing capacity of the beam, while the degradation of the corroded rebar had a significant effect. Under moderate and severe corrosion conditions, the bearing capacity and ductility degradation caused by bond-slip are dominant in the mechanical property degradation of the beam. Overall, the macroscopic mechanical properties of the corroded beam are influenced by the coupling effect of bond-slip degradation and the mechanical property degradation of the rebar. With the increase in the corrosion rate, the bearing capacity and ductility of the beam are decreased, and its brittleness is increased.