Objective Islets transplantation of pancreatic islets has been demonstrated to be a viable alternative to exogenous insulin therapy for diabets mellitus. However, it requires that the islets must have a good function. This study was design to investigate how to retain best the islet function in transplantation as cocultured with EFCs. Methods The EFCs were isolated from SD rat fetus and islets were purfied from SD rats. The viability of the isolated islets was assessed by AO/PI double staining. The islets were cultured alone(group Ⅰ), coculture with EFCs(group Ⅱ) and EFCs only(group Ⅲ). Islet viablity was assessed by mitochondrial activity and insulin release assay. Results Morphology assay: Islets in group Ⅱ exhibited excellent morphology, with greater than 95% staining positive as detected by AO/PI. Insulin release assay showed that: There was significantly a higher simulation indece(SI) in group Ⅱ as compared with group Ⅰ(P<0.05) except the first day. Mitochondrial activity: A total of the absorbance of the islet cells by MTT in 3,5,7,14 day between group Ⅰ and group Ⅱ showed significant difference(P<0.05, or P<0.01).Conclusion This preliminary series of controlled experiments suggest that cocultrue of