Digital geological mapping technology has comprehensively promoted the application of the national regional survey since 2004,which using the PRB data from the process of digital geological mapping to build shallow 3D geological model which has an important significance. The key of building 3D geological model is the construction of 3D geological interfaces. This paper focuses on the building process and the method of six kinds of major geological interfaces of the fault plane, the quaternary system interface, formation interface, rock interface, residual lid interface and xenolith interface. The first step of building surfaces is building the boundary surface of the model(DEM surface, bottom boundary and four peripheral interface),and then building the fault plane, finally building other geological interface according to the order of geological which should follow the principle of \"field line data as the main data ,subsurface geological data as the constrained data\". The geological interface building with the method can be perfectly consistent with the subsurface geological data, and creating geological interface with high precision and beautiful, but it can be limited by surface attitude. Although this method applies only to build shallow 3D geological model, the model can be used as a reference and constrain of deep 3D geological model. Modeling units can not only be the same as geological mapping units, but can undertake a combine a small amount of merger. The model can reach high precision which depends on the accuracy and quantity of the field mapping data, especially of the field route point of the line and effective attitude. In order to guarantee the precision of the model, it should try to ensure the boundary of each field line has an effective attitude and at the location of the geological boundary large changing needs to increase the data of attitude in the process of field lines mapping.