In　this　paper,　we　adopted　the　first-principles　calculations　to　investigate　the　sensing　properties　of　the　GeP　monolayer　to　four　SF6　decomposition　gas　molecules　(H2S,　SO2,　SO2F2　and　SOF2).　By　discussing　the　calculated　adsorption　energy,　charge　transfer,　work　function　variation　combined　with　charge　density　difference　and　electron　localization　function　analysis,　we　find　that　GeP　monolayer　exhibits　favorable　adsorption　strength　to　SO2　molecule　with　the　most　intense　charge　interaction.　And　SO2　adsorption　can　remarkably　change　the　density　of　states　(DOS)　of　GeP　monolayer.　Furthermore,　we　also　study　the　adsorption　performance　of　SO2　molecule　on　GeP　monolayer　under　applied　biaxial　strain　and　external　electric　field.　And　the　results　demonstrate　that　applying　negative　electric　field　can　significantly　enhance　the　sensitivity　of　GeP　monolayer　to　SO2.　Therefore,　GeP　monolayer　is　a　potential　candidate　for　highly　sensitive　and　selective　tunable　SF6　decomposition　gas　sensor　for　on-line　diagnostics　of　power　equipment.　©　2001-2012　IEEE.