Abstract: In this paper, combining with the characteristic of macroscopical fissure in engineering rock mass, the authors study the modeling technology of random fissure by Autocad and Ansys. Firstly, the authors compile program of random fissure by VB, and realize the random fissure in Autocad. Secondly, the authors switch it to the model which Ansys could recognize, then design by the numbers in Ansys. Thirdly, the authors import the fissure model into FLAC^3D for numerical simulation. According to the analog results, the plastic zone extends because of random fissure, and rock mass may be liable to destroy. In a word, the method of modeling technology of random fissure is feasible.