Background: Acute Coronary Syndrome (ACS) is a very common cardiovascular disease in clinical practice with a very high risk of death. In this study, we observed the effectiveness of CT angiography (CTA), matrix metallopro-teinase-9 (MMP-9) and platelet-activating factor (PAF) in the assessment of ACS. Methods: A total of 124 patients with ACS admitted to our hospital from June 2022 to March 2024 were enrolled as study subjects. All study subjects were examined using coronary angiography (CAG) and CTA. To compare the detection rate of ACS by CAG and CTA and the difference in effectiveness in assessing coronary plaque stenosis and plaque calcification. In addition, the levels of MMP-9 and PAF were detected in the patients to analyze their relationship with the degree of stenosis and plaque grade. Subsequently, the effect of the three combined tests, CTA, MMP-9 and PAF, was analyzed to assess postoperative vessel restenosis. Finally, we examined the factors associated with poor CTA image quality. Results: There was no difference in the effectiveness of CTA in detecting ACS, assessing coronary plaque stenosis and plaque calcification compared with CAG (P>0.05). There was a positive correlation between MMP-9, PAF and the degree of coronary stenosis and plaque severity (P<0.05). The diagnostic accuracy of the combination of CTA, MMP-9, and PAF in diagnosing stenosis in postoperative ACS was 97.58% (Kappa=0.946). It was determined that 124 patients and 21 patients had poor CTA images, and logistic regression analysis showed that shorter breath-hold time and arrhythmia were independent risk factors for poor CTA image quality. Conclusions: CTA, MMP-9 and PAF are excellent for diagnosing stenosis after ACS, and shorter breath-hold time and arrhythmia are all independent risk factors for poor CTA image quality.