Abstract: In the context of China's increasingly prominent compound and cross-regional air pollution issues, the traditional territorial governance model is no longer adequate to address these challenges. There is a need to shift from administrative boundary constraints towards the promotion of regional air pollution collaborative governance. This study first analyzed the mechanism of action of air pollution collaborative governance policies and proposed research hypotheses. Further, based on panel data from 279 prefecture-level cities or above in China from 2013 to 2020, this study empirically explored the policy effects and mechanisms of regional air pollution collaborative governance using the Propensity Score Matching-Difference in Differences (PSM-DID) method. The findings revealed that: (1) Baseline regression analysis indicated that the implementation of collaborative governance policies significantly reduced urban AQI indices and concentrations of pollutants such as PM₁₀, SO₂, NO₂, and PM_2.5, thereby overall enhancing regional air quality. A series of robustness tests confirmed the reliability of these conclusions. (2) Regional heterogeneity analysis showed that the effects of collaborative governance in the Beijing-Tianjin-Hebei region were significantly better than those in the Yangtze River Delta region. (3) Mechanism analysis indicated that regional air pollution collaborative governance primarily improved regional air quality by promoting industrial structure upgrading, enhancing the level of technological innovation, and increasing investment in pollution source control. The study further proposed relevant policy recommendations.