Abstract: An improved elevation model of InSAR which expresses the direct relationship be-tween height and phase has been developed based on the InSAR elevation model of Currie and Baker.The errors introduced by the parallel ray approximation applied in the improved mod-el are analyzed,and the results verify that it can not be ignored for satellite radar system.The error propagation curves and the relation between elevation errors and baseline parame-ters are also given which can be used to rectify the approximation errors and reconstruct the high accurate digital elevation model(DEM).In addition,based on the improved model and error propagation law,an elevation error estimation formula is derived.It gives the definite effect of the baseline length and angle on the elevation accuracy.