Abstract: Based on the maximum principal stress criterion, the crack propagation of reinforced concrete three point bending beams are simulated with the XFEM (extended ˉnite element method). The accuracy and the effectiveness of the proposed method are veriˉed by comparing with the results of the existing model test. It is shown that the crack growth and the mechanical properties of the reinforced concrete members with cracks are not only affected by the size, the position, the inclination angle of the single crack, but also affected by the location of the cracks. The transverse and longitudinal distributions of cracks are the main factor that affects the crack growth path and the mechanical properties of the reinforced concrete beams with cracks.