The problem of three-dimensional crack propagation is analyzed by the numerical manifold method(NMM) and the corresponding program with C++ is produced. By fully taking advantage of NMM in the area of discontinuous deformation analysis

the concepts of level set(LS) and Heaviside function in the extended finite element method(XFEM) are not required to be used. The result obtained from NMM is used to analyze failure state of each crack tip line. The exiting nonlocal crack tracing method and triangle tracing method are simplified and extended; and then a new tracing method is proposed to determine the final crack face. A block with a horizontal penny-shaped crack under tensile loading is simulated. The results show that the 3D crack propagation simulation based on NMM is feasible. After the simplification and extension

the shortcoming of original algorithm is overcome. The numbers of new crack tip line and new crack face are greatly reduced; and the influence of mesh on new crack surface is reduced; therefore the computational efficiency can be improved and the application can be expanded.