Spaceborne Compact Polarimetric Synthetic Aperture Radar (CP SAR) is a new form of SAR, which has intrinsic advantages in maritime surveillance because it can obtain relatively rich polarimetric information of targets with wide swath. First, the basic modes and the development of a spaceborne CP SAR system are introduced in this paper with respect to ship detection applications. Second, typical methods of spaceborne CP SAR information processing are reviewed. Third, the attributes of frequently used methods for spaceborne CP SAR ship detection are analyzed and compared in depth. Fourth, the results of our research on spaceborne CP SAR ship detection are given. Finally, suggestions for further research on spaceborne CP SAR ship detection are proposed.