Based on panel data of 23 OECD countries from 1990 to 2015, this research empirically analyzes the impact of environmental policy strictness on air quality (proxied by PM2.5, CO2, NOx, and SOx emissions) and compares it to PM2.5 exposure using the method of System Generalized Moments (SYS-GMM). We further test the robustness of the empirical results by the methods of restricted samples period, cross-sectional regression, and Least Squares Dummy Variable Corrected (LSDVC) model. Overall, we find that environmental policy stringency (EPS) has a negative impact on CO2, NOx, and SOx emissions, while EPS presents a weak impact on both PM2.5 emissions and PM2.5 exposure, due to two potential reasons: first, the causes of PM2.5 are complex, and environmental policies are difficult to succeed; second, during the process of formulating the EPS composite index, there is no emphasis on the policy of PM2.5 restrictions. Overall, our empirical results confirm the role of environmental policy stringency and point out some shortcomings. •We analyze the impact of environmental policy strictness on air quality by using multi-national and multi-year data.•The robustness of the model is tested from many methods, which ensures the reliability of the conclusion.•We analyzed the reasons why EPS had no significant effect on PM2.5 emission, and enriched the relevant literature.•We put forward two channels of EPS affecting emissions, and give the improvement direction of EPS in the future.