Abstract: Modular construction technology of secondary system in intelligent substations refers to the use of modular technology to achieve standardized designing and factory processing, assembly-type construction, to enhance the overall efficiency and quality of construction. Prefabricated optical cables between equipments, cabins, and prefabricated cabin or chamber using standard sequence of pins are an important part of the modular construction technology. Summarizing the experience of modularized intelligent substation construction in recent 3 years, this standard focuses on the number and pins definition of prefabricated optical cables between intelligent cabinets and prefabricated cabin or secondary equipment rooms in Smart Substation, in order to achieve the standardization of prefabricated cable used in intelligent substation project.