D-InSAR is currently one of the most popular research tools in the field of Microwave Remote Sensing. It is unrivaled in its aspect of measuring ground deformation due to its advantages such as high resolution, continuous spatial-coverage and dynamics. However, there are still a few major problems to be solved urgently as a result of the intrinsic complexity of this technique. One of the problems deals with improving the accuracy of measured ground deformation. In this paper, various factors affecting the accuracy of ground deformation measured by D-InSAR are systematically analyzed and investigated by means of the law of measurement error propagation. At the same time, we prove that the ground deformation error not only depends on the errors of perpendicular baselines as well as the errors of the interferometric phase for topographic pair and differential pair, but also on the combination of the relationship of perpendicular baselines for topographic pairs and differential pairs. Furthermore, a feasible approach for improving the accuracy of measured ground deformation is proposed, which is of positive significance in the practical application of D-InSAR.