As all countries pay more and more attention to marine security and territorial issues， underwater laser communication plays a more and more important role. The realization of high-speed transmission and confidentiality of information in a complex marine environment is an urgent subject for underwater laser communication. This paper sorts out the development history of underwater laser communication systems at home and abroad， summarizes their technical advantages， gives their communications principles， analyzes the key technologies influencing the system''s performance. Finally， the future underwater laser communication systems will not only possess high communication rate， low bit-error rate， long transmission distance， large capacity， low power consumption， and small size， but also develop from point-to-point communication to network-type communication.