Abstract: In order to improve the accuracy of DEM (digital elevation model) acquired by airborne InSAR (synthetic aperture radar interferometry), we researched the orthogonal decomposition of visual vector model and three dimensional reconstruction model for airborne InSAR. Error sources and adjustment parameters of domestic airborne InSAR system of CASMSAR (synthetic aperture radar system of Chinese Academy of Surveying and Mapping) were analyzed. A block adjustment method was proposed for airborne InSAR which could be used to derive DEM. An Experiment was carried out with X-band interferometric data acquired by CASMSAR. And we used ground control points to correct this error model. The results show that the proposed algorithm could be used to eliminate the differences in plane and height among multi-strip in the overlapping area. Finally, the results met the requirements of topographic mapping at a scale of 1:10 000, and proved the correctness and effectiveness of the new algorithm with CASMSAR data.