The invention discloses a connecting device for multi-fiber prefabricated outdoor optical cables of an intelligent transformer substation. The connecting device comprises the outdoor optical cables, and is characterized in that multiple prefabricated branches are directly guided out from the optical cables by branching devices, protection sleeves are disposed on outsides of the prefabricated branches, and an optical connector is disposed at the end of each prefabricated branch. By the aid of the connecting device, the optical cables among devices of the intelligent transformer substation are directly connected without joints formed by welding, jumper connection and the like, and construction intensity and complexity are greatly reduced.