Abstract： Objective To study the effectiveness of IL-4 on type 1 diabetes in NOD mice and it’s possible mechanism.Methods 4-week-old NOD mice,as a kind of type 1 diabetes model,were treated with IL-4 to investigate the incidence of insulitis,and lymphocyte subsets were determined by FACS.Results The incidence of diabetes in the IL-4 group was 12.50% which was obviously less than 62.50% in the control group ( P <0.05),and the degree of insulitis in the IL-4 group was also less than that in the control group.The lymphocyte subset in the IL-4 treated group showed higher CD + 4/CD + 8 cells and percentage of IL-2R + cells in spleen,and higher proportion of CD + 4/CD + 8 but decreased CD + 4/CD + 8 cells in thymus.Conclusion IL-4 can prevent NOD mice from developing type 1 diabetes,which may be related to the fact that IL-4 corrected the imbalance of immunoregulatory in NOD mice.