Objective To compare the plaque composition and burden between patients with acute coronary syndrome (ACS) and those with stable coronary artery disease (SCAD) using quantitative plaque assessment with coronary computed tomography angiography (CCTA). Methods A total of 116 patients in the Department of Cardiology, First Medical Center, Chinese PLA General Hospital from January 2021 to March 2021 were retrospectively included, who were divided into the ACS group (n=81) and the SCAD group (n=35) according to the clinical diagnosis. All the patients underwent CCTA and coronary angiography within 14 days after the diagnosis. A CCTA software for plaque quantification analysis was used to measure such imaging features as plaque component volume and burden, minimal lumen diameter (MLD), remodeling index (RI), and eccentric index (EI). SPSS 20.0 was used for statistical analysis. Depending on the data type, data comparison between two groups was performed using t-test, Wilcoxon test or χ²test.Results The ACS patients had higher total plaque burden (TPB), non-calcified component burden (NCPB), and lipid component burden (LPB), the differences being statistically significant[(60.5±11.2)% vs (51.7±14.4)%,(58.9±12.0)% vs (50.1±15.2)%,17.9%(11.6%,27.6%) vs 14.2%(7.5%, 20.8%),all P<0.05]. There was no significant difference between the two groups in plaque component volume, calcification component burden (CPB), RI and EI. In the ACS patients, the culprit lesions had higher TPB, NCPB and LPB than the non-culprit lesions[(62.3±10.4)% vs (54.8±10.6)%,(60.7±11.0)% vs (52.4±11.0)%,(19.7±10.3)% vs (15.1±9.2)%,all P<0.05)]. In addition, the culprit lesions had smaller CPB than non-culprit lesions[0.5%(0.0,2.6)% vs 1.5%(0.3,3.6)%,P<0.05]. Conclusion Quantitative CCTA analysis of the coronary plaque composition revealed that patients with ACS and culprit lesions show higher TPB, NCPB and LPB.