Objective To study clinical detection value of 64 multi-slice CT to plaques composition of patients with acute coronary syndrome(ACS). Methods 84 patients with coronary heart disease treated in our hospital from May 2013 to January 2015 were selected as the research objects, all patients underwent 64 multi-slice CT coronary angiography examination, selective coronary angiography examination(SAG), electrocardiographic examination, SAG results were served as the gold standard, sensitivity, specificity and accuracy of 64 multi-slice CT in the forecast of coronary artery stenosis were estimated, patients were divided into ACS group and non ACS group according to 64 multi-slice CT inspection results at the same time, coronary plaque analysis software was used to analyze plaques composition, plaques type, plaques composition, plaques CT value, changes of CT value after delayed sweep in the two groups were compared. Results Sensitivity of 64 multi-slice CT in the forecast of coronary artery stenosis was 96.83%, specificity was 80.95%, accuracy was 92.86%; plaques composition analysis showed that there was no significant difference in Ⅰ type plaques proportion in the two groups (P>0.05), there was a significant difference in Ⅱ type and Ⅲ type plaques proportion in the two groups(P<0.05), lipid composition of plaques in ACS group (66.74±5.28)% was significantly higher than non ACS group (P<0.05), fiber content (31.49±1.28)% and calcification composition (4.79±1.28)% of ACS group were significantly lower than non ACS group(P<0.05), plaques CT value, CT value after delayed sweep, decreased value of ACS group were significantly lower than non ACS group (all P<0.05). Conclusion 64 multi-slice CT can identify plaque form of ACS patients effectively, identify its stability, is worth for application in clinical experience.