As a kind of modern vehicle, subway has shown us the advantages of safety, speediness, low power consumption, low pollution etc. It has been the main part of the urban high-capacity public traffic system. More and more subway lines appear in order to meet the need of the society. The civil engineering construction especially in Soft Ground must lead to the deformation of the adjacent subway tunnel, and it causes the severe influences to the stabilization and safety of the tunnel. This paper puts forward a kind of three-dimension deformation monitoring method. It can precisely monitor the deformation of the tunnel liner real-time which do not interrupt the subway transport, and expediently provide mechanics analysis on the deformation of tunnel construction. The paper discusses how to build the 3D mathematical model for the subway tunnel by the ground lidar surveying technology. Use the Georobot to survey the deformation of the tunnel cross section and the rail automatically. According to data processing and analysis using a model interpolation method, the 3D digital model of the deformation and displacement for the whole metro is fitted finally. Thus we can obtain the 3D image of the subway deformation in a precision, real-time, stereo and visual way.