Abstract: 3D geological model is the major breakthrough of transition from traditional 2D to 3D space for the expression of geological survey information. At present, 3D geological mapping in China is being carried out as an important basis for deployment of geological survey work. During the process, combining the investigation and research is of great significance promoting the conversion of 3D geological modeling from research to practice. How to accurately and quickly build 3D faults model is one of the key points and difficulties. Through analyzing the data source at different stages of digital mapping and using relationship mapping rules between faults data and field data about the primitive data map, the 3D faults modeling method from line to surface is proposed and implemented. This method emphasizes that the faults modeling process is coincident, dynamic and fast. The data used in the building model come from the first hand field data. The method makes full use of the association, constraints and inheritance relationships at different stages of mapping, which can meet the requirements of rapid and dynamic rebuilding of model by the progress of geological understanding in the mapping process, and can also verify the rationality of connecting boundaries constantly. The algorithm was tested with several field experiments in the actual 3D geological mapping, with satisfactory results achieved. Experiment shows that the 3D fault modeling method based on primitive data map synchronizes with the actual business process, operates conveniently and can satisfy the practical requirements of 3D geological mapping.