Complex portal structure has to be adopted for tunnels on highspeed railways so as to minimize the aerodynamic effect induced by the highspeed trains. In this paper, 3D modeling method is established for the complex tunnel portal structure of highspeed railways by using the “Sketch Tracer” function of CATIA and on basis of 2D CAD method. The method mentioned is easy to be conducted, and the 3D model established can meet the requirements of the design parameters. The method has great significance for the 3D model show and Computational Fluid Dynamics (CFD) works.