Objective To study the difference in thrombus formation at distal end of the graft with two different treatments.Methods For coronary artery bypass grafting with distal-end side-to-side anastomosis (DESSA), two models with or without distal end trimming of the graft were established. Using the blood substance transport and diffusion model considering biochemical reactions, combined with hemodynamics parameters of shear rate, fluid residence time, and platelet distribution, the possibility of thrombus formation was evaluated. Numerical simulation method was used to investigate thrombus growth in coronary artery bypass grafting with DESSA.ResultsFor the model without distal end trimming of the graft, the thrombus was first formed on inner wall at distal end of the graft, and then grew inward until the thrombus occupied most of the graft region at distal end, which indicated that thrombus formation was in a stable state, and the volume of the thrombus didn’t change, the final volume of the thrombus was 15.05 mm3. For the model with distal end trimming of the graft, the final volume of the thrombus was 7.35 mm3, which was 51.2% smaller than that of the model without distal end trimming of the graft. Thrombus was formed on inner wall of the graft above the anastomosis for the model with distal end trimming of the graft, and the wall thickness was about 0.16 mm, which was 10.65% of the graft radius (1.50 mm). In the above two procedures, multiple vortices (blood flow velocity less than 10 mm/s) were formed in distal region of the graft, which further promoted thrombus formation at distal end of the graft. The area of thrombus formation obtained from numerical simulation was consistent with clinical investigation.Conclusions For clinical coronary artery bypass grafting with DESSA, the volume of the generated thrombus can be reduced for the model with distal end trimming of the graft. However, the effect of thrombus formation on inner wall of the graft above the anastomosis on coronary artery bypass grafting needs further study.