In　order　to　more　effectively　monitor　the　ultra-high　frequency　(UHF)　partial　discharge　of　gas　insulated　switchgear　(GIS),　the　design　technology　of　GIS　internal　disc-type　UHF　sensors　is　optimized　in　this　paper.　Firstly,　the　internal　UHF　sensor　simulation　models　of　the　GHz　transverse　electromagnetic　(GTEM)　equivalent　height　and　the　return　loss　parameter　(S11)　are　built　respectively.　The　influences　of　hand　hole　and　internal　sensor　structure　parameters　on　detection　performance　parameters　are　studied.　The　experimental　results　of　sensor　performance　are　compared　with　simulation　results.　The　results　show　that,　with　the　increment　of　the　diameter　of　the　hand　hole,　the　resonant　frequency　decreases　gradually.　The　sensor　equivalent　height　is　inversely　proportional　to　the　hand　hole　depth.　As　the　increment　of　electrode　diameter,　the　lowest　resonant　frequency　gradually　decreases.　And　the　thinner　the　electrode　is,　the　more　favorable　the　signal　reception　of　the　sensor　is.　Finally,　the　optimization　internal　sensor　is　designed,　and　its　average　equivalent　height　is　14.0　mm,　which　is　basically　consistent　with　the　simulation　equivalent　height　curve.　The　experimental　results　show　that　the　detection　sensitivity　of　the　optimized　sensor　is　better　than　that　of　the　commercial　sensor.　©　2020,　High　Voltage　Engineering　Editorial　Department　of　CEPRI.　All　right　reserved.