Abstract: Objective: To explore the correlations between the plasma levels of enzyme chitin 40(YKL-40),high-sensitivity C-reactive protein(hs-CRP),uric acid(UA) and coronary lesions in patients with acute coronary syndrome(ACS).Methods: One hundred and two patients with acute coronary syndrome(ACS) identified by coronary arteriography including 48 cases of acute myocardial infarction(AMI) and 54 cases of unstable angina pectoris(UAP) and 52 healthy adults were divided into the ACS group and control group,respectively.The ACS group were divided into the single-vessel lesion subgroup(43 cases),double-vessel lesions subgroup(37 cases) and multi-vessel lesions subgroup(22 cases) according to the number of coronary artery lesions.The plasma levels of YKL-40,hs-CRP and UA in two groups were measured by enzymelinked immunosorbent assay(ELISA).Results: The differences of the plasma levels of YKL-40,hs-CRP and UA between the AMI patients,UAP patients and control group were statistically significant(P< 0.01).With the increasing of the number of coronary artery lesions,the levels of YKL-40 and hs-CRP in ACS group increased.The differences of the levels of UA in the subgroups of ACS group were not statistically significant(P >0.05),but for the levels of YKL-40 and hs-CRP,its differences were statistically significant(P< 0.01).The plasma levels of YKL-40,hs-CRP and UA were positively correlated with the number of coronary artery lesions(P< 0.05).Conclusions: The level of YKL-40 increasing can hint the unstable status of coronary artery in ACS patients,which is closely associated with the coronary heart disease and its severity.