Space-borne platforms are indispensable for sea target surveillance. Multi-source information fusion can improve the accuracy of detection, confidence of recognition, coverage of spatial-temporal and reduce the fuzziness of inference. To improve the capability of maritime target wide-area searches, accurate identification, persistent surveillance and operational response, both space-based maritime target surveillance systems and multi satellite information fusion need to be further studied. The characteristics of maritime environment and maritime target for maritime target information awareness and fusion are reviewed and the developments, data characteristics and disadvantages of current space-based maritime surveillance systems are summarized. The key technologies and future development of space-based maritime surveillance are discussed in the fields of satellites networking, temporal-spatial fusion and information fusion.