Due to the volume expansion of corroded rebar products, the cracking of the concrete cover would occur, and has a serious impact on the durability of the concrete structure. In this paper, a numerical model was established for the simulation of the corrosion of rebar in concrete structures with the aid of finite element analysis software. The distribution of stress in concrete around rebar, that due to the expansion of these corroded rebar products, was obtained. The theory of elasticity method is used to validate the distribution of stress in concrete around rebar. The location of cracks would be predicted by the distribution of stress in concrete around the rebar.