Research　has　shown　that　there　is　huge　amount　of　transfer　of　carbon　emissions　embodied　in　trade　(CEs-ET)　between　developed　and　underdeveloped　regions,　which　causes　equity　and　efficiency　losses　in　carbon　emission　(CE)　reduction.　The　exploration　of　effective　approaches　to　mitigate　CEs-ET　transfer　and　promote　CE　reduction　has　become　worldwide　hot　but　difficult　issues.　This　research　innovatively　introduced　the　polarized　and　trickling-down　effect　in　development　economics　and　the　environmental　externality　theory　in　environmental　economics　into　the　study　of　CEs-ET　transfer,　and　demonstrated　that　the　net　CEs-ET　inflow　to　developed　regions　from　underdeveloped　regions　is　actually　the　polarized　effect　of　＇carbon　emission　space　(CES)＇　of　developed　regions　on　underdeveloped　regions　caused　by　regional　economic　development　gaps.　To　reduce　CEs-ET　transfer　and　promote　the　overall　CE　reduction,　it　is　required　to　formulate　regional　collaboratively　implemented　environmental-economic　policies　from　the　perspective　of　increasing　interregional　cooperation,　to　reduce　the　CES-polarized　effect　and　improve　the　CES-trickling-down　effect.　Next,　we　chose　the　typical　and　representative　region　in　study　of　CEs-ET　transfer,　the　Jing-Jin-Ji　region,　as　case　studies,　to　illustrate　the　CES-polarized　and　CES-trickling-down　effects　based　on　the　latest　2002–2017　interregional　input-output　(I–O)　data.　By　applying　the　models　of　emissions　embodied　in　bilateral　trade　(EEBT)　and　structural　decomposition　analysis　(SDA),　we　evaluated　the　evolution　of　the　CES-polarized　effects　in　the　Jing-Jin-Ji　region　and　their　driving　mechanism.　We　found　that　Beijing　and　Tianjin　had　an　obvious　CES-polarized　effect　on　Hebei,　the　Beijing-Hebei　and　Tianjin-Hebei　CES-polarized　effect　firstly　strengthened　and　then　weakened,　and　was　highly　concentrated　in　a　few　industries　such　as　electricity　steam　and　hot　water　production　and　supply　(ElectpowerProd),　metals　smelting　and　processing　(MetalSmelt),　and　Coal　mining　and　processing　(Coalmin).　Scale　and　technology　were　the　key　driving　factors,　but　for　different　industries,　scale　and　technology　functioned　differently.　The　trickling　down　of　technology　and　scale　in　the　Jing-Jin-Ji　region　produced　a　CES-trickling-down　effect　and　restricted　further　aggravation　of　the　CES-polarized　effect.　Subsequently,　we　established　a　coupling　relationship　(CR)　model,　which　comprehensively　compared　the　economic　and　environmental　effects　of　adjusting　the　trade　value　of　an　industry.　Finally,　by　combining　the　industrial　CES-polarized　effect,　the　SDA　results,　and　the　CR　results,　we　identified　the　key　regulating　industries　and　put　forward　the　Beijing-Hebei,　Tianjin-Hebei,　and　the　Jing-Jin-Ji　collaboratively　implemented　optimization　policies,　to　reduce　the　CES-polarized　effect,　improve　the　CES-trickling-down　effect,　and　promote　the　collaborative　CE　reduction　in　the　Jing-Jin-Ji　region.　This　research　could　enrich　the　theoretical　connotation　and　driving　mechanism　analysis　of　the　formation　and　evolution　of　CEs-ET　transfer,　and　provide　a　new　reference　for　the　formulation　of　an　effective　and　cost-effective　regional　collaboratively　implemented　CE　reduction　scheme　between　developed　and　underdeveloped　regions.　©　2022