Objective：This study aims to observe the effects of n - 3 poly unsaturated fatty acids（n - 3 PUFA）on immunological functions of T cells in NOD mice. Methods：Spleen cells were separated from Balb/c WT mice and NOD mice. The CD4+ T cells were obtained from magnetic bead separated spleen cells and divided into four groups：wild type group，NOD mice untreated group（control）， NOD mice treated with（docosahexaenoic acid，DHA）and（eicosapentaenoic acid，EPA）groups. The NOD mice T cells were treated with EPA and DHA respectively for 24 h. After the stimulation and activation of PMA and lonomycin，the viability of T cells was tested by CCK-8 kit，the differentiation of Th cells was analyzed by flow cytometer，and the secretion of inflammatory cytokines was measured by ELISA Kits. Results：EPA and DHA could inhibit the viability of T cells from NOD mice，suppress the naive T cells’differentiation into Th1 cells，balance the ratio of Th1 and Th2，and down-regulate the secretion of IL-6 and IL-17. Conclusion：n-3 PUFAs could suppress some immune functions of T cells by inhibiting their viability，regulating the Th1/Th2 polarization and inhibiting the secretion of IL-6 and IL-17.