Aircraft relay can quickly build an end-to-end communication network, enhance the coverage and transmission capacity of the communication system, strengthen the signal receival and improve the data transmission speed, and improve the reliability of the communication system. This paper summarizes the development status of UAV relay technology and UAV relay in wireless optical communication at home and abroad, and conducts in-depth research on the key technologies of UAV relay in wireless optical communication. The channel characteristics and their influence on communication and suppression techniques are analyzed, the advantages and disadvantages of different modulation and demodulation methods and the specific methods of beam capture, tracking and alignment in the communication process are compared, and the fast alignment of the beam is introduced in detail. Finally, the development direction of UAV relay in wireless optical communication is prospected.