Abstract: Phase unwrapping of the interferometric SAR is a very important step to obtain an accurate DEM (Digital Elevation Model). By using a recurrence estimating method, this paper describes a kind of method for phase unwrapping of INSAR. Starting from given initial phase values or adjacent unwrapped phase, the phase estimation values are sequentially obtained by the recurrence relation. Then by the measure of confidence of the phase estimation valuse, the unwrapping phase values of high reliability can be obtained. By using the approach, the simulating experiment is undertaken. The result shows that the method successfully unwraps the phase and the error caused by the algorithm is also very small.