The transport sector is the fourth largest industrial CO 2 emitter in China, next to power sector, iron and steel industries, and nonmetallic mineral product industry, and plays an important role in reducing China’s CO 2 emissions. In this study, a temporal decomposition analysis model, i.e., Logistic Mean Division Index (LMDI), is developed to analyze the influencing factors of CO 2 emissions in China’s transport sector during 2000–2015. Then, a multi-regional spatial decomposition model is employed to identify the key factors to induce the differences in CO 2 emissions of China’s 30 regional transport sectors in 2000, 2005, 2010, and 2015. Based on the empirical results, we find that both in the temporal and spatial perspectives, the main factors that affect CO 2 emissions in the transport sector are the same ones. From the temporal perspective, the income effect is the dominant factor increasing CO 2 emissions of transport sector, while energy intensity effect and transportation structure effect are the key influencing factors that curb the CO 2 emissions of China’s transport sector, during the whole study period. From the spatial perspective, the income effect, energy intensity effect, and transportation structure effect are the key influencing factors that enlarge the gap of CO 2 emissions of various transport sectors in the key study years. More importantly, the less-developed regions and high energy intensity regions (i.e., the lower energy efficiency regions) are identified to have the great potential to reduce CO 2 emissions of transport sector. Therefore, differentiated mitigation measures and interregional collaborations are encouraged to reduce transport sector’s CO 2 emissions in China.