Corona　performance　is　an　important　factor　should　be　taken　into　consideration　in　power　transmission　project　designs.　Power　equipments　operate　in　various　environments　which　will　affect　their　corona　inception　voltages　and　thus　influence　the　operation　safety　of　transmission　systems.　In　this　paper,　corona　characteristic　tests　of　bus　bars,　shielding　rings,　simulated　eight-bundled　conductors,　and　insulators　were　carried　out　in　areas　with　different　altitudes　up　to　4300　m.　Simulation　tests　of　environmental　factors　were　carried　out　in　a　HVDC　corona　cage.　Based　on　site　tests,　it　is　concluded　that　corona　inception　voltages　of　both　bus　bar　and　shielding　ball　increase　with　their　height　to　the　ground　or　their　dimensions.　The　influences　of　water　droplet,　wind,　icing　and　surface　contamination　on　corona　inception　voltage　were　also　obtained　from　the　simulation　tests.　The　corona　inception　voltage　of　mist　is　higher　than　that　in　saturated　water　droplets.　Conductivity　of　precipitation　has　little　impact　on　corona　discharges.　Corona　inception　voltage　decrease　with　increasing　wind　speed.　The　influence　on　corona　current　of　glaze　is　the　biggest,　and　that　of　hard　rime　is　more　than　that　of　soft　rime.　The　impact　of　pollution　material　on　corona　discharge　depends　on　the　size　of　pollution　particle.　Test　results　obtained　in　this　paper　are　solid　reference　for　design　of　UHV　DC　transmission　projects.