Objective To investigate the value of coronary CT angiography (CTA) in diagnosing the nature of plaques in patients with acute coronary syndrome (ACS). Methods Thirty patients with ACS treated in the department of cardiology of the hospital from April 2015 to April 2018were selected as the study subjects. Thirty patients with stable angina pectoris (SAP) were selected as controls. All patients underwent CTA examination and quantitative parameters were compared between the two groups. The sensitivity, specificity, positive predictive value and negative predictive value of CTA in the diagnosis of ACS vulnerable plaques were calculated. Results The non-calcified plaque burden and remodeling index(RI) in ACS group were significantly higher than those in SAP group (P<0.05), and the CT value of plaque minimal density was significantly lower than that in SAP group (P<0.05). There was no significant difference invascular volume, total plaque volume, non-calcified plaque volume, calcified plaque volume, calcified plaque load or degree of lumen stenosis (P>0.05). The incidence of the minimum CT value <35HU and positive remodeling (RI>1) in ACS group were significantly higher than those in SAP group (P<0.05). The sensitivity, specificity, positive predictive value and negative predictive value of the minimum plaque CT <35HU and RI>1 in diagnosing ACS vulnerable plaques were 73.33%, 90.00%, 88.00%, 77.14% and 80.00%, 76.67%, 77.42% and 79.31%, respectively. Conclusion CTA plays an important role in differentiating the plaque load between ACS and SAP. The CT value <35HU andRI >1suggestvulnerable plaques.