Abstract: Undersea junction technology is one of the core technologies for building a cabled ocean observatory system， which connects multiple devices underwater to manage the power and information. The undersea junction technology started earlier in United States， Japan， Canada and other country， which gradually developed negative high-voltage single-stage DC power transmission， high-power power conversion， underwater wet plug， large-scale optical fiber communication networking and other technologies. Using modular design and multi-level junction box interconnection， large subsea observatory has been built in many sea areas. In the past decade， with the domestic development of offshore ocean observation system， junction box design and high voltage power transmission， remote communication and control technology has developed rapidly， the scientific nodes undersea junction boxes have been successfully applied in a number of sea areas， but has not yet formed a large observatory. Some of the deepwater key components such as underwater wet plug connectors， cables are mainly dependent on imports. While introducing and absorbing foreign advanced technology， the development of high-performance controllers， high-power conversion modules， underwater connectors and photoelectric complex cables will be a very important direction of the future junction boxes.

Key words: junction box, ocean observatory, undersea transmit electricity, telecommunication, underwater wet-mate connector