Abstract: Increasing attention has been focused on the extent to which corporate political connections influence the growing pollution due to the rapid growth in the popularity of firm pollution in developing countries. We adopt a static threshold regression model to investigate the effects of heterogeneous environmental regulation on political connections and firm pollution based on the panel data from China’s A-share listed companies from 2012 to 2019. The empirical results show a non-linear relationship between the degree of political connection of listed company executives and the level of firm pollution. And the relationship between the two roughly presents a U-shaped relationship under the action of the market-incentive environmental regulation threshold. However, it roughly presents an inverted N-shaped relationship under the action of the command-control environmental regulation threshold. Additionally, the group test results show that the existence of regional and ownership heterogeneity causes certain differences in the environmental behaviour of politically connected enterprises. These findings indicate that diverse environmental regulations are needed to promote sustainable green development and to further expand the theoretical and practical exploration of political connections on firm pollution.