The space optical communications have gone through decades of development, evolving two generations of optical communication terminals, and accomplishing several on-orbit experiments. The overall development history of space optical communications is summarized, the development progress of Europe, Japan and the USA is introduced in detail, and then some of the typical terminals and experiments are stressed, as well as the key technologies. The development status in China is briefly introduced. The development trends of space optical communication are analyzed, and the technical challenges are pointed out.