Objective To detect and analyze the percentages of CD4+T, CD8+T and invariant na-ture killer T ( iNKT) cells as well as iNKT subsets in different tissues and organs of non-obese diabetic (NOD)/LtJ mice before the onset and in the early and late stages of type 1 diabetes (T1D) for better under-standing the immune function in different disease stages. Methods Female NOD/LtJ mice were selected as experimental subjects. Their fasting blood glucose levels were measured by blood glucose meter. Glycosuria and blood glucose level ≥11. 1 mmol/L in two consecutive detections were used as the diagnostic criteria of T1D. These mice were divided into three groups as follows: non-onset, early stage and late stage groups. Changes in food and water intake, glucose level in the urine, body weight, mental state, fur color and urine volume were recorded. Percentages of CD4+T, CD8+T and iNKT cells and ratios of subsets in peripheral blood, thymus, spleen, liver and inguinal lymph nodes were detected by flow cytometry (FACS). Results (1) Compared with the non-onset and the early stage groups, mice in the late stage group were apathetic and had rough hair. Moreover, significantly increased water and food intake and urine output (P<0. 05) and de-creased body weight, thymus index, spleen index and the absolute lymphocyte counts of spleen, liver and thymus (P<0. 05) were observed in the late stage group. (2) Compared with the non-onset group, the early stage group showed significantly increased percentages of CD4+T cells in spleen, liver, thymus and inguinal lymph nodes (P<0. 05). Compared with the early stage group, the late stage group showed decreased per-centages of CD4+T cells in liver, thymus, inguinal lymph nodes and peripheral blood (P<0. 05). Compared with the non-onset group, the percentages of CD8+T cells in the early stage group were significantly increased in spleen and thymus, but reduced in inguinal lymph nodes (P<0. 05). Compared with the early stage group, the percentages of CD8+T cells in late stage group were significantly reduced in liver and thymus, but increased in inguinal lymph nodes (P<0. 05). (3) The percentages of iNKT cells in liver and inguinal lymph nodes of mice in the early stage group were significantly higher than those of the non-onset group (P<0. 05). The percentages of iNKT cells in peripheral blood and liver of mice in the late stage group were sig-nificantly lower than those of the early stage group (P<0. 05). No significant difference in the percentages of iNKT cells in spleen and thymus was found among the three groups (P>0. 05). (4) Compared with the non-onset group, the percentages of iNKT1 subset in thymus in the early and late stage groups were significantly increased, while the percentages of iNKT2 subset were significantly decreased (P<0. 05). No significant difference in the percentages of iNKT1 and iNKT2 subsets in spleen, liver and inguinal lymph nodes was found among the three groups (P>0. 05). (5) The percentages of iNKT2 subset in spleen, liver and ingui-nal lymph nodes were significantly lower than those of the iNKT1 subset in the three groups (P<0. 05). The percentage of iNKT2 subset in thymus was significantly higher than that of iNKT1 subset in the non-onset group (P<0. 05). (6) Compared with the non-onset and the late stage groups, the early stage group showed significantly increased levels of IFN-γ, IL-4 and IL-17A and up-regulated ratio of IFN-γ/IL-4 (P<0. 05). Compared with the non-onset and the early stage groups, the late stage group showed significantly increased IL-6 level (P<0. 05). Compared with the non-onset group, IL-10 level in the other two groups was in-creased, especially in the late stage group (P<0. 05). No significant difference in IL-2 level was found among the three groups (P>0. 05). Conclusion Increased percentages of iNKT cells and iNKT1 subset in NOD/LtJ mice with early stage of T1D might be involved in the development of T1D.