There is an urgent clinical for small diameter vascular grafts (SDVGs) for use in the treatment of coronary artery disease. Moreover, biodegradable SDVGs are drawing increasing attention because they have the potential to restore vascular function with the degradation of vascular graft and tissue regeneration. In this study, we designed triple-layered SDVGs to mimic the native arterial structure, with each layer contributing its unique porosity to the porous structure. We evaluated triple-layered SDVGs in a sheep carotid arterial replacement model. After implantation for 12 months, two grafts were patent and indicated the feasibility of using grafts in large animals. Nevertheless, it was determined that both grafts formed aneurysms at the proximal end. The prevention of such aneurysms remains a challenge for future investigation.