At present, there exist many simple and reliable methods to describe the damage degree of reinforced concrete structure induced by low velocity impact. However, the actual fracture process can not be well reflected by the current methods. Therefore, a piece part model, which can well describe the damage process, was put forward. The cracks generated in the concrete beam can be reflected by the interfaces between the elements. In this method, the beam is descretized as the linking system of the steel bar and concrete. The dynamic calculating equation of the beam is deduced on the basis of the internal force and inertia force of the rigid unit and linking piece. The local deformation in the contact region of the beam and the stress-strain state of the beam under low velocity impact can also be calculated by this method. Finally, the advantages of the model were proved by a practice example.