Abstract: Based on Digital Elevation Mode (DEM) data, satellite orbit and baseline information, a kind of fast interferometric phase simulation method is investigated and presented for spaceborne multi-baseline InSAR system. By taking advantage of forward geocoding, the match of DEM model under strict spaceborne InSAR geometry is utilized to realize multi-baseline interferometric phase generation, and the match process is further optimized by polynomial approximation and hybrid iteration. Theory analysis and simulation experiments indicate that the proposed method can improve the computation efficiency with enough phase accuracy, as well as better iteration convergence property for complicated DEM model. Consequently, the method is suitable for efficient simulation of spaceborne multi-baseline InSAR interferometric phase for large and rugged terrain.