Bushing　is　an　indispensable　component　in　high　voltage　direct　current　(HVDC)　transmission　project.　As　the　main　insulating　material　possesses　poor　thermal　conductivity　and　negative　temperature　coefficient　(NTC)　electrical　resistivity,　HVDC　bushing　suffers　from　the　distortion　of　electro-thermal-coupled　fields.　Therefore,　it　is　urgent　to　reveal　the　influence　of　electrical　resistivity-temperature　characteristic　and　thermal　conductivity　on　the　DC　electric　field　distribution　within　bushing　insulation,　guiding　the　design　and　application　advanced　insulating　materials.　Here,　the　simulation　of　temperature　and　DC　electric　field　distribution　within　a　400　kV　bushing　are　carried　out.　The　results　show　that　the　optimization　of　NTC　effect　and　thermal　conductivity　of　an　insulating　material　is　able　to　obtain　a　more　uniform　electric　field　distribution　through　homogenizing　the　electric　resistivity　distribution　within　bushing　insulation.　The　activation　energy　of　the　insulating　material　has　a　similar　variation　trend　with　the　maximum　electric　field　within　bushing　insulation,　which　has　a　potential　to　represent　the　temperature　dependence　of　electrical　resistivity　of　insulating　materials.　It　also　shows　that　the　reduction　of　DC　electric　field　by　increasing　the　thermal　conductivity　has　a　saturation　feature.　As　a　result,　the　suppression　of　the　NTC　effect　should　be　considered　together　to　obtain　a　smaller　electric　field　within　HVDC　bushing.　The　research　study　provides　a　new　idea　to　regulate　the　DC　electric　field　distribution,　which　is　beneficial　to　the　design　of　advanced　insulating　materials.