Abstract: To study the crack propagation of a reinforced concrete beam, a three-dimensional model of a simply supported concrete beam with an embedded crack was established. Based on the extended finite element method (XFEM), a cohesive crack model was used to describe the mechanical behavior of the crack surfaces. The stain softening behavior of a fracture process zone of the crack tip was represented by a linear softening curve. The mixed-mode fracture process of a plain concrete beam and reinforced concrete beam were simulated. The influences of longitudinal reinforcement on the crack propagation, load-deflection curve and load-CMOD (Crack Mouth Opening Displacement) curve were analyzed. The numerical simulation results show a good agreement with the experiment results. The advantage of XFEM for the structural analysis of fracture failure was presented.