In order to express the relationship between geology and tunnel engineering directly and accurately, a 3D geology and tunnel modeling method is studied. Firstly, a normalized three-dimensional geological body model reconstruction method based on the geological horizontal cross-section is proposed. And then, the model cutting and stratification during the merging process of tunnel horizontal cross-section-based 3D modeling and the model of tunnel and geology are studied based on the established 3D geological model. Finally, a horizontal cross-section-based 3D tunnel geological modeling and visualization system is developed. The modeling example shows that the method mentioned above can achieve good 3D geology and tunnel modeling results, visually demonstrates the relationship between the tunnel and the strata, and shows the internal details of the tunnel.