With the deepening exploration of space by humans, traditional radio frequency (RF) communication increasingly fails to meet the demands of high-speed deep space communication. Various spacefaring nations have undertaken research on deep space optical communication technology. Optical communication is a crucial means of achieving space communication. Compared to traditional RF communication, optical communication offers advantages such as high communication speed, small terminal payload, strong anti-interference capabilities and so on, making it more suitable for ultra-long-distance deep space communication. Currently, the United States leads in research and has successfully conducted two deep space optical communication demonstrations. This paper provides a comprehensive review of existing research plans and demonstration results in deep space optical communication. It analyzes the key technologies for implementing deep space optical communication, reflects on the developmental history, and contemplates the future prospects of deep space optical communication.