Objective To investigate the revascular and transplanted effects of islet grafts after co-transplantation with vascular endothelial cells ( ECs) in diabetic rats. Methods The rat ECs and islet cells were isolated and purified, then subcutaneously co-transplanted to the inbred SD male rats with diabetes mellitus, the group of islets transplanted alone, group of phosphate buffered solution, and group of normal rats served as control. Islet grafts revascularization degree, islet cells activity and apoptosis were observed by immunohistochemical double staining of CD31, insulin and factor associated suicide (Fas) antibody. The results of intraperitoneal glucose tolerance test (IPGTT) and intraperitoneal insulin tolerance test (IPITT), the blood glucose and insulin levels of the rats and the survival time of the islet grafts were compared. Results The blood glucose concentrations of IPGTT and IPITT, the blood glucose and insulin levels of rats analyzed by multivariate analysis in the ECs and islets transplantation group were better than those in the islets transplantation alone group (P<0.05). The islet grafts mean survival time of the ECs and islets transplantation group was longer than that of the islets transplantation alone group (P<0.05). On the 7th day after transplantation, mean microvascular density of islet grafts per square millimeter in the ECs and islets transplantation group was 26.4 ± 6.1, significantly greater than that in the islets transplantation alone group 18.3 ± 5.7 (P<0.05). In the ECs and islets transplantation group, insulin staining intensity was higher than that in the islets transplantation alone group (P<0.05), while factor associated suicide(Fas) staining intensity was lower than that in the islets transplantation alone group ( P<0. 05 ). Conclusion Co-transplantation with ECs could promote the revascularization of islet grafts and improve the effect of islet transplantation.