Trade drives increased life-cycle carbon dioxide (CO2) emissions and carbon leakage from plastics, increasing the environmental burden on the supply chain. Therefore, assessing the characteristics and drivers of plastic carbon emissions will help develop emission reduction strategies from a supply chain perspective. In this study, we present a model framework for life-cycle assessment, optimized input-output analysis, and structural decomposition analysis. Specifically, for the first time, we assess the life-cycle CO2 emissions of plastics in China, the world's largest producer and consumer, and consider the input, production, consumption, and income stages of the plastic supply chain. China's plastic CO2 emissions increased by 38.07% from 2010 to 2021 and, under a business-as-usual path, will consume 4.2–5.4% of the global carbon budget by 2050. From a supply chain perspective, each economic sector assumes different responsibilities for emissions at different stages. Despite increasing emissions, China's economic structure has potentially improved the embodied carbon leakage from the intersectoral and international trade in plastics. Furthermore, regarding socioeconomic factors, the levels of final demand (63%) and primary input (61%) dominated the increase in plastic CO2 emissions from 2012 to 2020, and the intensity of emissions was the key to reducing emissions. The novelty of this study is that the model we proposed can solve the data limitations of the global plastics supply chain and focuses for the first time on the input and income stages and their drivers.