In this present single-center, prospective study, by analyzing the circulating lipid profile and the major adverse cardiovascular events (MACEs) among ACS patients with or without DM, we aimed to evaluate the relationship between the HDL-C/apoA-I ratio and the severity of coronary artery stenosis and also to explore the short-term prognostic value of the HDL-C/apoA-I ratio in ACS patients. Here, APOA1 is linked to diabetes mellitus.