Digital twin is a new technical means to realize the interactive integration of the physical world and the information world. It has been widely used in many business fields and has received more and more attention. Based on the analysis of the connotation and architecture system of digital twin, this paper discusses its key technologies in model construction, data collection and analysis, virtual-reality interaction and visualization, summarizes the research progress of digital twin technology in hot fields such as intelligent manufacturing, smart cities, mining, power monitoring and water conservancy projects, summarizes the existing deficiencies and future development trends, in order to provide reference and inspiration for the development of digital twin technology.