Abstract: Based on intensive analysis of the relationship between interferometric coherence and Doppler frequency difference, we propose an algorithm for spaceborne interferometric SAR signal processing with coherence optimization. Different from those traditional SAR processing algorithms, the basic idea of this algorithm is the Doppler parameters in SAR signal processing should be equalized for interferometry. Although signal-noise-ratio (SNR) may be lowered, the coherence between the two SAR images can be improved. Therefore, interferograms with better quality can be acquired by employing the proposed method. The level 0 and level 1 products of ERS-1/2 Tandem datasets in Zhangbei has been tested. The results show that the quality of interferogram from level 0 data processed with the proposed method is better than that from standard level 1 data provided by ESA. The experimental results indicate the proposed method is highly desirable for research and application for InSAR technology.