Reinforcement corrosion is the primary cause of the failure of marine concrete structures. Thus, it is necessary to explore the development of corrosion expansion stress and the process of induced concrete cracking, which is beneficial to the service life prediction of reinforced concrete. In the experiments, the reinforcement corrosion in mortar is accelerated by adding salt and using constant potential. The strain in the reinforcement corrosion process is monitored by the strain gauge attached to the stainless steel ring outside the mortar to calculate the corrosion expansion stress. The COMSOL software is used to analyze the development of corrosion expansion stress in concrete and the whole concrete cracking process induced by reinforcement corrosion. The results show that the finite element method and the time-varying radial displacement loading method can be used in simulating and testing the corrosion expansion and cracking process of reinforced concrete respectively, the results of which are basically consistent. Without considering the inhomogeneity of mortar and reinforcement and the filling effect of corrosion products on cracked mortar, the simulation results fail to reflect the fluctuation and the process of release and gradual increase of corrosion expansion stress. In addition, by increasing the mortar strength and decreasing the reinforcement diameter, corrosion expansion and cracking of reinforcement can be effectively delayed.