The invention discloses an underwater photoelectric separation structure which comprises a shore base station, a photoelectric separation cavity, a power supply cavity and a control cavity, wherein electric energy and an optical communication signal provided by the shore base station are accessed into the photoelectric separation cavity through a photoelectric composite cable; the electric energy and the optical communication signal are separated inside the photoelectric separation cavity; the separated electric energy is accessed into the power supply cavity through a watertight cable; the optical communication signal is accessed to the control cavity through the watertight cable; the photoelectric separation cavity comprises a cavity body, end covers and a sealing structure; the end covers are arranged at two ends of the cavity body respectively; the sealing structure is arranged inside one of the end covers; the photoelectric composite cable is fed into the sealing structure and is used for implementing photoelectric separation through the photoelectric separation structure. By adopting the underwater photoelectric separation structure, direct connection of the photoelectric composite cable and the power supply cavity or the control cavity is avoided, the power supply cavity or the control cavity can be prevented from damage caused by phenomena such as damage of the photoelectric composite cable, water seepage of a cable feeding cavity sealing structure, and the like, economic loss caused by the problems can be reduced, and very high application values can be made for development of seabed observation network techniques.