Interferogram noise filter is one of the key technologies which use synthetic aperture radar interferometry phase to extract digital elevation model. However, the interference fringes’ details are often reduced when complex interferogram is filtered, and this leads to inaccurate phase unwrapping result, for this combined filter method based on terrain factors is proposed. Filter method can be selected through weight factor associated with the terrain slope in the filter process, and Wiener filter method is implemented in flat terrain area, frequency estimated filter method is achieved in steep terrain area. Then the new filter method is applied to deal with data where the region of Quebec, Canada. This proves that the new filter algorithm proposed in this paper can effectively suppress noise and better maintain stripe details.