Abstract: This paper investigates the impacts of the uncertainties of phase measurement, orbits and topography on the products of repeat-pass InSAR, Two-pass DInSAR and Three-pass DInSAR, respectively.The sensitivity of deformation with respect to phase measurement errors is about 3 000 times lower than that of topography to phase measurement errors.The longer the effective baseline is, the less the impact of the uncertainty of baseline on heights is.For a small area (e.g.5 km), a moderate DEM accuracy (e.g.16m) can be reached be using the baseline with an accuracy of 1m, only if the effective baseline is moderate (e.g.200 m).But for a large area, a baseline accuracy of 5 cm should be expected in topography mapping.