Large amount of CO₂ is generated from numerous production chains, which exists between the final demand of transportation and the intermediate demand of each production sector. Certain key sectors and production chains bear a greater responsibility for reducing these CO₂ emissions. To explore this problem, this study investigates China’s transportation CO₂ emissions based on the multi-layered structural paths by utilizing the environmental input–output model and the structural path analysis method. Several crucial findings are revealed from our analysis. Firstly, the CO₂ emissions resulting from transportation final demand and intermediate demand display a significant upward trend. Secondly, four major CO₂ emitting sectors are identified. Thirdly, the key production chain paths of transportation demand leading to CO₂ emissions are found. Finally, the study concludes emphasizes that the efforts to reduce CO₂ emissions in the transportation sector should focus on the key sectors and production chains in the transportation sector.