Numerical models based on FLAC 3D are difficult to build. A new kind of method modeling and meshing in the CATIA software, named the CATIA-FLAC 3D coupled modeling method, was proposed. This method utilizes the powerful geological modeling capabilities of CATIA for three-dimensional geological body modeling and meshing. And then, the interface program of CATIA-FLAC 3D is adopted to export the information into FLAC 3D, which is coded by visual basic language based on the variance of nodes and elements between the two software. The new proposed method was used in a bias tunnel through a mountain, and the results verified the feasibility and effectiveness of the proposed method.