Abstract: The security mechanisms for terrestrial network are not appropriate for satellite communication due to the particularity of space environment. The state of the art in security for satellite communication systems was surveyed. Firstly, the security vulnerabilities of satellite communication systems were presented. Secondly, various possible threats and countermeasures were analyzed among physical layer, data link layer, network layer and transport layer. Particularly, representative solutions for survivability, anti-jamming, authentication and key management were illustrated, and a comparison and assessment of their merits and faults were made. Finally, the research was presented which was still worth to do in the future.