Identifying　CO2　emission　from　different　perspectives　is　necessary　for　developing　the　effective　mitigation　policies　for　China.　Previous　studies　mainly　focus　on　exploring　important　sectors　from　production　and　consumption　sides,　while　the　perspective　of　betweenness　has　been　neglected.　For　narrowing　the　gap,　a　new　perspective　for　accounting　the　critical　transmission　sectors　is　discussed.　In　this　study,　we　calculated　and　compared　the　CO2　emissions　of　production-based,　consumption-based,　and　betweenness-based　from　2012　to　2017　based　on　the　multi-regional　input-output　(MRIO)　model.　A　structural　decomposition　analysis　(SDA)　is　conducted　to　uncover　the　driving　forces　of　CO2　emissions　change　from　three　accounting　principles.　The　Findings　are　as　follows:　(1)　the　heavy　industry　sector　(559.26　Mt)　in　Shandong　and　Jiangsu　(471.97　Mt),　Power　in　Guangdong　(83.77　Mt)　and　Beijing　(199.24　Mt),　Equipment　in　Jiangsu　(213.88　Mt)　are　identified　as　the　key　transmission　sectors;　(2)　the　emission　intensity　effect　and　the　final　demand　product　structure　effect　contribute　to　CO2　emission　decrease　in　China,　which　are　largely　offset　by　the　structure　effect　of　final　demand　source　and　the　final　demand　scale　effect.　Based　on　this,　we　propose　some　typical　policy　implications,　such　as　paying　close　attention　to　the　production　efficiency　of　the　key　transmission　sectors,　optimizing　the　intermediate　product　input　structure　and　increasing　investment　in　the　technology　level,　and　then　reducing　the　intensity　of　carbon　emission.