This article takes the balanced panel data of 30 provinces (cities, autonomous regions) in China from 2007 to 2022 as the research sample(excluding Xizang, Hong Kong, Macao and Taiwan regions.), and systematically examines the impact mechanism of environmental regulations on carbon emission intensity from the perspective of green tax. The study incorporates industrial upgrading, green technology innovation, and low-carbon energy index into the analysis framework, constructs theoretical models and empirical testing systems, and deeply explores the transmission path of green tax policies on carbon emission intensity. The empirical results show that: firstly, through a two-way fixed effects model regression, it was found that green tax has a significant positive effect on reducing regional carbon emission intensity. Further testing with the mediation effect model shows that this emission reduction effect is mainly achieved through three indirect paths, namely promoting the transformation of industrial structure towards low-carbon, incentivizing the research and application of green technologies, and enhancing the low-carbon level of energy consumption structure. Secondly, regional heterogeneity analysis reveals significant spatial differences in the emission reduction effects of green tax, with negative and significant impacts in some regions. There is a negative but not significant impact in the southern coastal, northwestern, and northeastern regions. There is a positive impact in the eastern coastal areas and the middle reaches of the Yangtze River. Thirdly, time heterogeneity analysis shows that, taking 2018 as the boundary, the emission reduction effect of green tax in the later stage is more significant than that in the earlier stage, which is closely related to the implementation of environmental protection tax, the improvement of green tax system, the enhancement of policy execution ability, and the strengthening of market entities’ adaptability in 2018.