The most serious problem after implantation of vascular graft is the formation of intravascular thrombus. In order to solve this problem, the scientific community has made various attempts over the past years. However, the fundamental way to resolve this problem to keep the vascular open for a longer period is endothelialization. There are two ways to realize endothelialization. One is implanting endothelial cells in vitro. Nevertheless, cells after implanting are always too weak to sustain blood flow, thus most of the cells will be washed away. Furthermore, cells culturing and implanting are always time-consuming and during this process contamination is easy to happen. Therefore, this method is not feasible in clinic emergency. The second way is in vivo endothelialization. This method succeeded in animal models including dog, pig, sheep, rabbit and rat. Unfortunately, it stays a problem in clinic. Poly (ε-caprolactone) as a degradable material show good biomechanical behavior and has been widely used in tissue engineering, drug delivery, and artificial grafts. After giving a brief introduction of PCL, this article reviews the current status of endothelialization for PCL small-diameter vascular graft implanted in healthy / pathological animals.