Abstract: Objective To investigate the correlation between serum chitinase 3 like 1 (YKL-40) and the severity of atherosclerotic plaque in patients with coronary heart disease (CHD). Methods Two hundred consecutive patients with CHD who underwent coronary angiography in the cardiology department of Chinese PLA General Hospital were recruited from January 1, 2015 to October 1, 2017. Serum YKL-40 was assessed in all patients. Meanwhile, Syntax score and quantitative coronary angiography were used to measure the severity of coronary stenosis. Results The YKL-40 level of low, moderate, high Syntax score group was(136.18±14.00) mmol/L, (158.36±12.39) mmol/L, (181.18±12.94) mmol/L, respectively. The level of YKL-40 increased with the severity of atherosclerotic plaque. Pearson correlation test showed that the level of YKL-40 was positively correlated with the degree of coronary stenosis (r=0.808, P＜ 0.05). Conclusion This study shows that the level of YKL-40 in patients with coronary heart disease is correlated with the degree of stenosis of atherosclerotic plaque. YKL-40 can be used as a biomarker to evaluate the degree of coronary stenosis.