Purpose: To evaluate image quality, and diagnostic accuracy of patients with percutaneous coronary intervention (PCI) in low radiation-dose and contrast dose coronary CT angiography (CCTA), using invasive coronary angiography (ICA) as the reference. Materials and Methods: This study obtained the approval of ethics committee. One-hundred thirty CCTA patients were randomly divided into the low radiation and contrast dose group (group A) and routine dose group (group B) with 65 cases in each group. All patients underwent prospective ECG-triggered CCTA examination. Patients in Group A were scanned with 100 kV with injection of 270 mg-l/ml contrast medium, while patients in group B were scanned 120 kV with injection of 350 mg-l/m1 contrast. Image quality, radiation dose (ED) and contrast dose between the two groups were compared. The sensitivity specificity, PPV, NPV and accuracy in-stent restenosis (ISR) were calculated and compared between the two groups. Results: Among the 107 measurable stents in group A, there were 14 stents among the 107 measurable stents in group A (13.1%) with ISR diagnosed by ICA. The specificity, sensitivity, PPV and NPV, accuracy in the diagnosis of ISR were 89.2% (83/93) and 85.7% (12/14), 54.5% (12/22) and 97.6% (83/85), 88.8% (95/107), respectively, in group A. These values were 89.7% (78/87), 76.9% (10/13), 52.6% (10/19) and 96.7% (78/81), 88.0% (88/100), respectively, in group B. There were good agreement in consistency between two groups and ICA, as the Kappa value were 0.61 and 0.60, respectively. The image quality of coronary artery and stent were not statistically significant (P > 0.05) between the two groups. Group A had significantly lower radiation (by 51.2%) and contrast dose (by 22.8%) than the routine dose group (P < 0.05). Conclusion: Both radiation dose and contrast dose may be reduced for patients after PCI while maintaining imaging quality and diagnostic accuracy.