Objective To investigate the relationship between the ratio of monocyte to lymphocyte and the severity and prognosis of non-ST-segment elevation myocardial infarction. Methods Two hundred and twenty patients with NSTEMI who underwent coronary intervention in Xintai People’s Hospital from June 2016 to September 2018 were selected. The clinical data of all patients were collected and followed up regularly for 12 months to record the occurrence of MACCE. SPSS 20 statistical software was used to process data. Results(1) Peripheral bloodmLR level was positively correlated with SYNTAX score of NSTEMI patients(r=0.575, P<0.05);(2) Multivariate COX regression analysis showed thatmLR, age, type 2 diabetes mellitus and hypertension were independent predictors of MACCE in NSTEMI patients;(3) ROC curve analysis showed that the area under the curve of predicting MACCE bymLR level in peripheral blood was 0.749(95% CI: 0.701~0.791), the best truncation value was 0.43, the sensitivity was 78.68%, and the specificity was 71.71%. Conclusion The level ofmLR in peripheral blood is positively correlated with the severity of coronary artery disease in NSTEMI patients, and it is an independent predictor of MACCE in NSTEMI patients. It can help to refine the risk stratification management of NSTEMI patients in clinical work.