After the pretreatment of neonatal rat islet-like cell clusters (ICCs) with irradiation of an excimer laser and an ultraviolet beam (UVB), the immunogenecity of islet was significantly reduced, especially in the excimer laser group. Morphological examination of the pretreated islets revealed that the secretory granules and subcellular structures remained intact, and the insulin secretion function of the pretreated islets showed no significant difference with that of the control group. The islet allotransplantation in STZ-induced diabetes rats indicated that the diabetes remission period of the rats of the excimer laser group was significantly longer than that of the UVB group and the control group.