Different surgical procedures in coronary artery bypass grafting (CABG) will cause different hemodynamic environments, which will affect the surgical result and long-term patency. In this study, the hemodynamic effect of the Y-type graft was discussed by comparing it with normal graft. A patient-specific 3-dimensional (3D) model of coronary artery with serious stenosis was reconstructed. Two different surgical procedures were applied on the 3D model through the virtual surgery, the normal graft and the Y-type graft. Thus, two 3D models with different grafts were built. The zero-dimensional (0D)/3D coupling method was used to perform the numerical simulation by coupling the 3D artery model with a 0D lumped parameter model of the cardiovascular system. The coronary flow rate and the graft flow were calculated and illustrated in this paper. The wall shear stress (WSS) and oscillatory shear index (OSI) were also calculated and depicted. The short-term outcomes of the normal graft and Y-type graft are almost the same. But the long-term patency of the Y-type graft is worse. Moreover, decreasing the diameter of the graft to LCX may get higher WSS and provide enough flow at the same time.