Abstract: The intelligent door technology of urban rail transit vehicle combines the door failure diagnosis and professional network technology, to implement information management, hazard analyse, failure diagnosis and failure prediction for vehicle door faults. In this paper, key technologies like the network structure, on-board monitoring equipment, intelligent door controller, door remote monitoring, door sub-health analysis,mobile maintenance, expert remote meeting, big data analysis and so on are elaborated, their application in rail transit lines of Chinese cities are introduced. The application of intelligent diagnosis technology shows that it can provide better support for the vehicle door system maintenance, improve the maintenance efficiency, the availability of train and the efficiency of rail transit line as well.