On the basis of expounding the internal mechanism of local government competition and scientific and technological innovation affecting carbon emissions, this paper analyzes, based on the provincial panel data from 2004 to 2019, the spatial characteristics of carbon dioxide emissions per unit of GDP in China, and empirically analyzes the impact of local government competition, scientific and technological innovation and their interaction on carbon emissions by using fixed effect model and threshold model. The research shows that the overall level of carbon dioxide emissions per unit GDP in China is decreasing, and the largest carbon emissions are in the northwest, while the smallest ones are in Beijing and the southeast coastal regions; Local government competition, scientific and technological innovation and their interaction have significant inhibitory effects on carbon emissions, and scientific and technological innovation has a threshold effect on carbon emission reduction driven by local government competition; Through the heterogeneity analysis, it is found that the effects of local government competition and scientific and technological innovation on carbon emissions are different in different economic zones and different industrial development levels. Therefore, we should make full use of the “competition for good” of local governments, strengthen the role of scientific and technological innovation in promoting carbon emission reduction, and promote industrial upgrading to achieve China’s sustainable development.