Objective To investigate the relationship between interleukin-18(IL-18)/interleukin-10(IL-10) ratio and the development of acute coronary syndrome(ACS) in stable angina pectoris(SAP) patients so as to provide new ideas for prevention of ACS. Methods The plasma IL-18 and IL-10 levels were measured by enzyme-linked immunosorbent assay in 215 SAP patients. The patients were divided into 2 groups: ACS group(group A, n=38) and non-ACS group(group B, n=173) according to the results of 24-month follow-up. Results Plasma IL-18 level and IL-18/IL-10 ratio were higher in group A than in group B[(229±77) vs (166±50) ng/L, (2.4±0.7) vs (1.6±0.6) respectively, P＜0.01]. Plasma IL-10 level was lower in group A than in group B[(101±37) vs (115±38)ng/L, P＜0.05]. Logistic regression analysis showed that high IL-18/IL-10 ratio increased the relative risk of ACS in SAP patients by 3.935 times(P＜0.01). Conclusion The plasma IL-18 and IL-10 levels are closely related to the development of ACS in SAP patients. Higher IL-18/IL-10 ratio is predictive of ACS development in SAP patients, which suggests that inflammation is an important enhancing factor for developing ACS, and anti-inflammatory treatment might be a new method for preventing ACS.