A new, fast, accurate and fullface deformation detection method based on highdensity 3D laser scanning technology, tunnel scanning and measuring system Tunnelscan, is introduced. The absolute positioning method （APM） of point cloud is used to register multiple scans and transfer the tunnel control coordinate system to them. The least square method based on minimum distance from crosssection points is used to calculate the center point of crosssection. A ringshape point cloud filter based on the distance difference from the measured crosssection and the referenced crosssection is applied to remove the noisy points that are actually not on the tunnel wall. The multiple loops of this ringshape filtering and center point calculation will be executed to get the refined center points and crosssection points of proper circular tunnel constructed by TBM method. It can also offer a new type of user report based on orthophoto of tunnel by laser intensity direction and ranging （LIDAR） of overall tunnel wall, which can provide a quick and big picture of tunnel diseases, such as crosssection deformation, structure clearance alarm, cracks or leakages, etc, using referenced crosssection contour projection method. A real 3D scanning asbuilt survey test in Majie StationMianshan Station section on Kunming Metro Line No.3 is carried out. With the abovementioned colorful overall tunnel map on the crosssection deformation analysis, much effort can be saved to find out those crosssection charts with large deformation. Apart from that, the analysis with orthophoto of tunnel is much more visual than that directly with 3D tunnel point cloud or that with 3D model for the shelter of visual angle.