Abstract: The basic formulation of solving congruence equations with Chinese Remainder Theorem (CRT) was introduced. And CRT was applied to phase unwrapping for dual-baseline InSAR. The congruence equations refer to interferometric phase fuzzy numbers were designed, and the phase unwrapping method for dual-baseline InSAR based on Chinese Remainder Theorem was proposed. In this algorithm, the un-fuzzy phase interval of phase unwrapping was extended, which helps to solve the difficult problem of phase unwrapping in sub-sampling area. The phase unwrapping experiments were done with simulated interferograms from different areas DEMs. The satisfying phase unwrapping results were gotten, as validated the phase unwrapping ability for the proposed algorithm in sub-sampling area.