Compared with full polarimetric, compact polarimetric Synthetic Aperture Radar(SAR) has the advantage of providing larger swath. Thus it is very useful in ocean monitoring. Aiming at maritime ship detection based on compact polarimetric spaceborne SAR imagery, this paper constructs compact polarimetric data under Circular Transmit-Linear Receive(CTLR) mode based on the Radarsat-2 full polarimetric data. Conventional extraction methods of spaceborne SAR compact polarimetric features are explored in this paper. The performance results on maritime ship detection based on spaceborne compact polarimetric SAR are obtained. The results show that the overall performance of the detection of compact polarimetric SAR closes to that of full polarization.