Objective:To observe the correlation of serum follistatin-like 1 (FSTL1) protein level and coronary artery disease in patients with acute coronary syndrome (ACS),and explore the clinical significance of serum FSTL1 level detection in patients with ACS. Methods:Among the total of 123 patients with ACS,25 patients with stable angina and the normal control group of 30 people were recruited. Serum FSTL1 level was measured by enzyme linked immunosorbent assay (ELISA),and the severity of coronary artery stenosis was measured by visual method and quantitative coronary angiography. The SPSS 17.0 software was used for statistical analysis. P value< 0.05 was considered statistically significant. Results:Serum FSTL1 level in all groups with ACS were significantly higher than that in the NC group and the SAP group (P < 0.01). Serum FSTL1 levels in patients with ACS were correlated the scope of coronary artery stenosis (P < 0.01). Serum FSTL1 levels (calculation the natural logarithm of serum FSTL1 levels,LnFSTL1) in the single-vessel disease group (2.38 ± 0.28),the double vessel disease group (2.43 ± 0.26),the multivessel disease group (2.57 ± 0.29) were significantly increased in turn. Moreover,there was statistical difference in each group (F = 5.25,P = 0.007). Conclusion:Serum FSTL1 levels in patients with ACS were significantly increased. The more serious the scope of coronary artery stenosis were,the higher serum FSTL1 levels elevated. Serum FSTL1 levels may have clinical value for the risk stratification and prognosis evaluation of ACS.