Abstract: Objective: To analyze the imaging findings of patients after coronary artery bypass grafting to evaluate whether or not there is a correlation between the transplanted vessels and the fractional flow reserve score of in-situ coronary artery. Methods: Retrospective or prospective analysis was performed on 29 patients who underwent CCTA after coronary artery bypass grafting, and FFR_CT value was measured on this basis to evaluate the degree of graft and in-situ coronary artery stenosis. Pearson correlation test was performed for the stenosis degree and FFR_CT value of the transplanted vessel and corresponding in situ coronary artery. According to whether the degree of stenosis of the transplanted vessels was > 50% or not, the two groups were divided into A and B groups, and the corresponding degree of stenosis of the orthotopic coronary artery lumen and FFR_CT value were respectively used for independent sample t test between the two groups. Results: Grafted vessels were negatively correlated with the degree of in-situ coronary stenosis, but positively correlated with the FFR_CT value of in-situ coronary artery. Compared with group A and Group B, the corresponding in-situ coronary plaque stenosis degree and FFR_CT value showed statistically significant differences in t-test results between the two groups. Conclusion: Grafted vessels are associated with the degree of orthotopic coronary artery stenosis, FFR_CT value and its evolution. The orthotopic coronary arteries compensate by diverting some of the blood flow from the grafted vessels when they become narrow.