Abstract:Based on the free stationing of the Intelligent Total Station, the formulas for computing the measurement errors of distance between arbitrary points have been established,and its analyzing software has also been developed. It has been considered that the measurement errors of distance is related not only to the oblique distance, zenith distance and horizontal vector, but also to the space position between the Total Station and measured points- The Total Station can be used to measure deformation of tunnel, but,if deformation is smaller, especially to operation tunnel,it is also available to use convergence gauge.