The central environmental protection inspection determined in 2016 aims to carry out innovative reforms in the form of environmental law enforcement and supervision. It is a major institutional arrangement for China to promote the construction of ecological civilization. Air quality is included in the inspection work by the Ministry of Ecology and Environment.Panel data from 256 prefecture-level and above cities across the country were used,and the quasi-natural experiment of the Central Environmental Protection Inspectorate were used, and the multi-period double difference method to evaluate the effect of improving air quality wre utilized. The results show that the central environmental protection inspector plays a significant role in reducing the air quality index, and the AQI of the inspected provinces has dropped by about 3.184 units on average; heterogeneity analysis shows that the central environmental inspector makes a significant contribution to the reduction of PM10, SO2, and O3 concentrations. But the improvement effect on PM2.5, NO2 and CO concentration is not obvious; further, parallel trend test, counterfactual test and propensity score matching test are used to prove the reliability of regression results. The dynamic effect analysis show that the policy effect of the central environmental protection inspector is lagging and weakened with the issuance of feedback.