Abstract:A method for analyzing tunnel deformation with the terrestrial laser scan(TLS)data based on the KNNSICP closing algorithm was proposed in the paper.First,the tunnel point cloud in the same area is extracted after registration.Second,the initial rotation and translation matrix are setted to unit and zero.The same slice of point cloud is closed by KNNSICP.At the last,the errors of corresponding points are calculated and the threshold is determined.The threshold is employed to extract the abnormal points before and after the deformation.The tunnel deformation would be determined by analyzing the changes of abnormal points.The results demonstrate the validity of the proposed method according to the example.