A highefficient portable laser range finder is developed so as to accurately measure the surface convergence/deformation of tunnel crosssection. The stability and calibrating capacity of the device are improved and the insitu measurement is realized by replacing the multiaxis joint lever by universal joint. The improved cross layout mode is used for measuring points; and BE measuring line is added. The calculation formulas of surface convergence/deformation of tunnel are deduced by small deformation principle and trigonometric function; and the relative displacement of tunnel surface sides to axial line and that of tunnel roof and floor are obtained respectively. Errors objectively exist in measuring; as a result, error processing should be carried out for singlepoint measuring and multiphase measuring. The true value of singlepoint measuring is estimated by average value of repetitive measured subsample data; and that of multiphase measuring is estimated by semiparametric regression method. The abovementioned device has been successfully used in Maluping Mine in Guizhou province for the first time; and the basic deformation rules of deep soft tunnel of the project have been obtained.