Nitrogen dioxide (NO 2 ) represents a deleterious effect on acute myocardial infarction (AMI), but few relevant studies have been conducted in China. We aim to evaluate the acute effects of NO 2 exposure on hospitalization for AMI in Lanzhou, China. In this study, we applied a distributional lag nonlinear model (DLNM) to assess the association between NO 2 exposure and AMI hospitalization. We explored the sensitivity of various groups through stratified analysis by gender, age, and season. The daily average concentration of NO 2 is 47.50 ± 17.38 µg/m 3 . We observed a significant exposure-response relationship between NO2 concentration and AMI hospitalization. The single pollutant model analysis shows that NO 2 is positively correlated with AMI hospitalization at lag1, lag01, lag02, and lag03. The greatest lag effect estimate occurs at lag01, where a 10 µg/m 3 increase in NO 2 concentrations is significantly associated with a relative risk (RR) of hospitalization due to AMI of 1.027 [95% confidence interval (CI): 1.013, 1.042]. The results of the stratified analysis by gender, age, and season indicate that males, those aged ≥65 years, and the cold season are more sensitive to the deleterious effects caused by NO 2 exposure. Short-term exposure to NO 2 can enhance the risk of AMI hospitalization in urban Lanzhou. Implications : Exposure to particulate matter can lead to an increased incidence of AMI. Our study once again shows that NO 2 exposure increases the risk of AMI hospital admission. AMI is a common and expensive fatal condition. Reducing NO 2 exposure will benefit cardiovascular health and save on healthcare costs.