Abstract: Objective To investigate the association of neutrophil to lymphocyte ratio (NLR) with coronary plaque composition assessed by intravascular ultrasound (IVUS) in patients with stable coronary artery disease (SCAD) and evaluate its predictive value on the vulnerable plaques. Methods A total of 243 patients with SCAD hospitalized in Chinese PLA General Hospital were included in the study from October 2013 to June 2016. Routine blood test was performed on admission and NLR value was calculated before coronary angiography. IVUS was performed on the culprit vessels to evaluate the component of coronary artery plaques. The correlations between NLR and the volume percentage of the main component of plaques were analyzed. According to the data from IVUS, the enrolled plaques were divided into two groups: vulnerable group and invulnerable group. The value of NLR in predicting the vulnerability of plaques was assessed by ROC curve. Results Univariate linear regression analysis showed lipid volume (r=0.32, P＜ 0.001) and fibrous volume (r=-0.43, P＜ 0.001) were correlated with NLR. In multiple regression analysis, NLR were independently associated with lipid volume (β=0.59, P=0.034) and fibrous volume (β= -0.22, P=0.004) in coronary plaques. A NLR=2.78 as optimal cut-off value had sensitivity of 77.6% and specificity of 74% (AUC: 0.789, 95% CI: 0.731- 0.846，P＜ 0.001) in predicting vulnerable plaques. Conclusion This study indicates NLR is linearly correlated with lipid and fibrous contents with larger plaque burden, which suggests that NLR can be used as a useful tool to predict plaque vulnerability in patients with SCAD.