To simulate the corrosion of reinforced concrete， chloride penetration was drove under constant potential. The effects of water to cement ratio， cover thickness， and steel bar diameter on the rust expansion cracking of specimens were studied. Additionally， the concrete model of real aggregate was established to simulate using COMSOL Multiphysics software. The results show that non-uniform corrosion of steel bar occurs and leads to three main cracks in concrete under constant potential accelerated corrosion. The rust expansion stress of concrete specimen is 2.85-3.51 MPa and the cracking time is 190-311 h in this experiment. Moreover， the cracking time of specimens can be delayed by reduction of the water to cement ratio and increase of the cover thickness. The numerical simulation can well reproduce the non-uniform corrosion process of reinforced concrete， and the evolution of rust expansion stress and crack development is consistent with the test results.