Abstract: Space-borne ISAR imaging technology has been regarded and studied gradually all over the world. The works are carried out in the paper aimed at a problem of mass data when some returned signal information is transmitted to the processors on the ground by spaceborne ISAR. A new method of ISAR data compressing and reconstruction based on Compressive Sensing (CS) is proposed. In the method, the returned signal is transformed spectrogram field which is range-slow time field, and the spectrogram is transmitted after it is compressed by using CS technology. Thus, the transmitted data can be reduced apparently. Next, the spectrogram information is recovered by using the orthogonal matching algorithm, and the ISAR image is reconstructed by using the method in the paper. Simulation results show that the reconstructed spectrogram is quite similar to the spectrogram uncompressed, and the fine ISAR image can be achieved by reconstructing. These works support a new idea to reduce data, improve efficiency in the ISAR signal processing.