Objective To investigate the relationship between the triglyceride glucose product(TyG)in-dex,plasma arteriosclerosis index(AIP),systemic immune inflammation index(SII),and the severity of acute coronary syndrome(ACS)and coronary artery stenosis degree in patients.Methods A retrospective analysis was conducted on patients who underwent coronary angiography at the hospital from November 2021 to De-cember 2023 due to suspected coronary heart disease,and they were divided into an ACS group(1 446 cases)and a control group(690 cases).General baseline and laboratory data of the patients were collected,and TyG index,AIP and SII in were calculated.Gensini score was used to evaluate the degree of coronary artery steno-sis.The risk factors of ACS were determined by binary multivariate Logistic regression analysis.Receiver op-erating characteristic(ROC)curve was drawn to analyze the diagnostic value of various indicators for the de-gree of coronary artery stenosis in ACS patients.Results TyG index,AIP and SII in ACS group were signifi-cantly higher than those in control group(P＜0.05).Binary multivariate Logistic regression analysis results showed that TyG index,AIP and SII were risk factors for ACS(P＜0.05).The ROC curve results showed that TyG index,AIP and SII had certain diagnostic value for the degree of coronary artery stenosis in ACS pa-tients.According to the cut off values of TyG index,AIP,and SII,the patients were further divided into differ-ent subgroups,the Gensini scores in the high TyG index,AIP,and SII groups were significantly higher than those in the low TyG index,AIP,and SII groups(P＜0.05).Conclusion TyG index,AIP and SII are closely related to ACS,which could be used as simple laboratory indexes for diagnosis of ACS,and also have good di-agnostic value for the coronary artery stenosis degree.