SF6 Gas-Insulated Metal-Enclosed Line (GIL) has the advantages of large transmitting capacity, low loss, small electromagnetic pollution for surroundings, strong capability to resist geological disasters, easy operation and maintenance, etc. In-depth research on the key technology of UHV GIL insulating part design, flexible line design, line manufacturing and detection, GIL installing on site and maintenance is the solid foundation for safe and reliable operation of UHV project.