Abstract: Against the backdrop of national industrial modernization and sustained economic growth, the demand for electric energy is continuously increasing. As a key device in the power system, substations play a crucial role in the transmission and distribution of electric energy. The safety, stability, flexibility, and economy of the power system largely depend on the quality of substation design. This paper takes the primary side main wiring design of a 110kV substation in an industrial park as the research object. Through consulting relevant materials, conducting research and analysis, and combining load calculations to determine transformer capacity, the main wiring scheme is designed. The research content includes main wiring design, selection of main transformers, short-circuit current calculation, and selection of electrical equipment. The specific work covers: (1) selection of main wiring scheme: 110kV single busbar sectionalization, 35kV single busbar sectionalization, and 10kV double busbar wiring; (2) selection of on-load tap-changer three-winding transformers and determination of winding wiring methods; (3) selection of main wiring scheme: 35kV single busbar sectionalization and 10kV double busbar wiring; (4) calculation of short-circuit current based on equivalent circuits; (5) briefly describing the principles of primary equipment selection.