FLAC3D is an excellent computer code for rock-soil mechanics numerical simulation, but it performs poor in modeling complex geological body. The features of modeling commands and * FLAC3D type file were elaborated, the space coordinate transformation and MLS interpolation method were introduced in detailed and a new modeling method was proposed and a computer aided modeling program was developed. The input of the program is just original data and does not need the aid of other commercial software. Through coordinate transformation and MLS interpolation, our method can quickly build complex geological model and is convenient to set material parameters and apply the stress boundary conditions, thereby can effectively improve the work efficiency.