A FE analysis model was made to simulate the whole process of cracking in RC beam due to the expansion of corroded reinforcement.The initiation and development process of cracking due to even and uneven expansion of corroded reinforcement were obtained,and the factors affecting the expansion rate at the time of cracking in the concrete cover were analyzed,including the thickness of concrete cover,rebar diameter and the concrete strength grade.The comparison of the experimental data with the previous research results indicated the same laws of corroded expansion.On this basis,the factors of structure durability and guided the design of structural durability were proposed.