Based on the panel data of 30 provinces in China from 2011 to 2021, this paper constructs two index systems to measure China’s carbon productivity (CP) and level of scientific and technological innovation (STI) respectively. The two-way fixed effect model, spatial Durbin model, and threshold effect model are used to explore the impact of STI on CP. The study found that: (1) STI can not only promote the improvement of local CP, but also have a positive spatial spillover effect on CP in surrounding areas; (2) The influence of STI on CP has regional differences, and STI in the eastern region has a significant positive effect on CP in both local and neighboring provinces; The STI effect is not obvious in the central and western regions. (3) The positive impact of STI on CP has the threshold characteristic of “marginal increasing” and there is a single threshold effect with STI and R&D intensity as threshold variables. The research conclusions provide empirical evidence for STI to promote the development of a lowcarbon economy, and have implications for the implementation of regional coordinated development and innovation-driven development strategies.