The application of gas-insulated line (GIL) connection was analyzed through techno-economic comparison, for the layout optimization of outdoor gas-insulated switchgear (GIS) substation. The result shows that this method has some advantages, such as economic in investment, little in occupy floor, reliable in connection, and it can promote the “resource conserving, environmental friendly and industrialized” substation construction. This paper put forward some proposals for the application of GIL connection, based on the deep analysis on the problems of using GIL connection during factory, handover preventive testing or maintenance.