In　order　to　reduce　the　greenhouse　effect　of　SF6　gas,　it　is　necessary　to　investigate　the　environment-friendly　gasinsulated　transmission　line　(EGIL)　with　free　SF6　gas　for　environmental　benefits　of　equipment.　From　three　aspects,　including　the　molecular　design　and　synthesis　of　preparation　for　environment-friendly　insulation　gas,　insulation　performance　and　gas-solid　material　compatibility,　1000kV　EGIL　prototype　development　and　operational　technology,　the　research　status　was　summarized　in　this　paper.　The　replacement　optimal　design　and　hybrid　design　method　for　new　substitution　environment-friendlygases　has　been　established.　The　proposal　of　insulation　design　basis　with　C4F7N　gas　mixture　was　provided.　The　support　insulators　and　pipeline　prototype　for　1000kV　EGIL　has　been　manufactured,　and　the　operation　and　maintenance　system　of　EGIL　was　set　up.　Some　main　problems　of　EGIL　to　be　resolved　further　has　been　put　forward,　including　the　synthesis　and　preparation　technology　for　new　environment-friendly　gas,　arc　extinguishing　and　its　recovery　characteristics　of　C4F7N　gas　mixture,　operation　and　maintenance　strategy　of　EGIL　et　al.　In　order　to　master　the　key　technology　of　C4F7N　environment-friendly　insulation　gas　and　its　application　of　equipment,　all　the　achievements　will　provide　the　beneficial　reference　for　the　development　and　operation　of　environment-friendly　electrical　equipment.　©　2020,　Electrical　Technology　Press　Co.　Ltd.　All　right　reserved.