Digital twin technology has the characteristic of virtual real fusion. The digital twin for intelligent factories can make the production process more transparent， and the production can be effectively guided with the real-time data in the workshop. In order to realize the visual control of production process based on the digital twin， a method of digital twin modeling for intelligent factories oriented to the production process is proposed. First， the framework of the digital twin system for intelligent factories is constructed. Second， the key technologies are elaborated， including the method of 3D geometric modeling based on the point cloud fitting， the method of object linking and embedding for process control unified architecture（OPC UA） information modeling for data interaction， multi-source heterogeneous data integration and fast matching of virtual-real mapping data. Finally， the digital twin system for an engine manufacturing workshop is realized. This demonstrates the correctness and effectiveness of the proposed method.