Abstract: China's carbon emissions have significant industrial and spatial concentration. Outward Foreign direct investment (OFDI) will change factor allocation and affect the layout of high emission industries and regions. Does the continuous expansion of OFDI promote China's carbon emission reduction? In this paper, the three main ways of OFDI affecting the carbon emission of the home country are first analyzed, namely, the economic scale, industrial structure and technical level, and the hypotheses to be tested are proposed. Secondly, selecting China's interprovincial panel data in 2005−2019, through multiple mediation effect models, empirically testing the three effects and comprehensive effects of OFDI on China's carbon emission. It is found that OFDI exacerbates the carbon emission of the home country to varying degrees through the economic scale and technical level intermediary mechanism, and the carbon emission of the home country is suppressed through the industrial structure intermediary mechanism; the economic scale and technical level effect are greater than the industrial structure effect, so China's OFDI ultimately aggravates the carbon emission of the home country. Finally, relevant policy recommendations are made based on conclusions.