Aim To investigate the correlation between monocyte to lymphocyte ratio (MLR) and lesion severity of coronary artery in patients with coronary heart disease (CHD) and its predictive value. Methods 203 patients with coronary angiography in the Department of Cardiology of Huayuan Mountain Branch of Hubei Provincial Hospital of Traditional Chinese Medicine from January to December 2018 were selected as the study subjects. 161 patients with CHD were divided into mild lesion group, moderate lesion group and severe lesion group according to the severity of coronary artery lesion (Gensini score). 161 patients with CHD were further divided into three groups according to the MLR three-quantile.In 42 cases of control group, coronary angiography showed that the normal coronary or stenosis degree of coronary artery was less than 50%. Logistic stepwise regression and receiver operating characteristic curve (ROC) were used to analyze the correlation between MLR and lesion severity of coronary artery in CHD patients and its predictive value. Results (1)Inter-group comparison of MLR three-quantile, coronary artery lesion score in the second three-quantile group and third three-quantile group was significantly higher than that in the first three-quantile group (P＝0.022, P＝0.001). (2)Spearman correlation analysis showed that MLR level was positively correlated with the severity of coronary artery lesions in CHD patients (r＝0.281, P＜0.01); Kendall correlation analysis also showed a positive correlation between MLR level and the severity of coronary artery lesions in CHD patients (r＝0.188, P＜0.01). (3)Logistic stepwise regression analysis showed that smoking history, old age, MLR and apolipoprotein B were independent risk factors for CHD, while apolipoprotein A1 was a protective factor for CHD. (4)ROC curve analysis showed that the area under curve of MLR was 0.709 (95%CI:0.621-0.797). When the cut-off value of MLR was 0.186, the diagnostic efficacy of MLR for CHD was the highest, with a sensitivity of 82.6% and a specificity of 50.0%. Conclusions Inflammation plays an important role in the pathogenesis of CHD. As an independent risk factor, MLR has predictive value for CHD.