Abstract: China’s socioeconomic development has undergone significant transitions. Exploring the socioeconomic factors affecting CO₂ emissions in recent years can support policymaking for CO₂ reduction in China in the post-epidemic era. Based on the structural decomposition analysis, we quantified the relative contributions of socioeconomic factors to CO₂ emission changes in China from 2017 to 2020. We also re-assessed the socioeconomic factors affecting CO₂ emission changes during 2010—2017 with revised official statistical data. Results show that changes in production structure and final demand structure contributed to CO₂ reduction from 2015 to 2017, while led to an increase in CO₂ emissions during 2017—2020. This finding indicates the potential of CO₂ reduction through the optimization of structural factors. We also find that the impact of socioeconomic factors (e.g., energy efficiency) on CO₂ emissions from 2012 to 2017 were different from existing studies. During 2012—2015, changes in energy efficiency were the driver contributing to CO₂ reduction, while the situation reversed from 2015 to 2017 due to unreasonable product structure in some sectors (e.g., the smelting and pressing of ferrous metals sector). Moreover, the impact of socioeconomic factors on CO₂ emissions had obvious sectoral heterogeneity. The production and supply of electric power and steam and smelting and pressing of ferrous metals sectors were relatively more affected. According to the above findings, this study proposes the following policy implications: (1) Adjusting the production structure of sectors such as petroleum processing and coking to promote CO₂ reduction of the whole supply chains, (2) further optimizing the investment structure and guiding consumers to use renewable energy, (3) optimizing the product structure and improving the proportion of high value-added products, (4) establishing cross-sector collaborative mechanism to promote CO₂ reduction of critical sectors.