This paper proposed a novel phase unwrapping method which unites beat-frequency localization, equivalent ground interferometric phase removing and ambiguity number estimation. First, a rough localization is conducted under the beat frequency with the information of beam pointing. Then, by introducing the technology of ground interferometric phase removing in interferometric synthetic aperture radar(InSAR), an equivalent approach is used to alleviate the pressure of phase unwrapping. At last, the ambiguity number is estimated by statistic processing. The practical data processing results showed that the proposed method can not only solve the relative phase wrapping caused by large target size, but also obtain the absolute phase, making three-dimensional(3-D) localization and 3-D imaging possible.