Abstract: This paper presents a crack model of reinforced concrete using a strain decomposition method to overcome the defect of a traditional smeared crack model. By the decoupling of normal and tangential strain of a crack plane, the constitution was constructed with nonlinear fracture mechanics respectively. Both the axial stiffness and the transverse stiffness were calculated in the reinforced concrete element after cracking. The transverse stiffness of a reinforcement bar was analyzed by the calculation model of an elastic grade beam. The proposed model was implemented in the nonlinear element analysis program with FORTRAN language. The rationality and validity of the model were assessed critically by comparing test results and numerical analysis of a classic reinforced concrete beam and a plane, and a good agreement was found. The proposed crack model can be employed in the nonlinear and the ultimate capacity analysis of reinforced concrete structures.