A coupling modeling method with MIDAS/GTSFLAC3D was put forward aiming at the technical difficulties and deficiencies in preprocessing for complex geologic body and structural engineering with FLAC3D. The coupling procedure was that, firstly, the threedimension geometry model was built with MIDAS/GTS and the model meshes were divided. And Secondly, the element and node data of the completed model built in MIDAS/GTS were exported. After data was transformed by using the interface program in MATLAB, the information was imported into FLAC3D. Thus the threedimension FLAC3D model for complex engineering was generated coupling with MIDAS/GTS. With coupling method, the complex threedimension model was built for Fanshuigou bridgeShipogou tunnel engineering above minedout region, and the results verified the feasibility and effectiveness of the proposed method.