Abstract: The phase noise suppression methods applied on the interferogram of interferometric synthetic aperture radar(INSAR) are studied.Multilook average approach(low pass linear filter) is discussed,and the new concept of range and azimuth critical look number used in multilook approach is proposed and its calculation formulas are deduced.The modified neighborhood field average filter,modified median filter and mode filter are analyzed,and a new practical method,which combines multilook average and nonlinear filter to reduce noise in the wrapped phase map,is presented.At the end of this paper,the characteristics of these approaches are compared and the experimental results by processing ERS-1/2 data are used to confirm that the method is more effective in suppressing noise in the interferogram of INSAR.