ObjectiveTo evaluate the effect of suppressive oligodeoxynucleotides (Sup ODN) on expression of Tbet, pSTAT4 and pSTAT6 of CD4+T spleen lymphocytes in vitro．MethodsThe spleen lymphocytes of BALB/c mice were isolated and then CD4+T cells were purified with immunomagnetic microbeads(positive selection),the purification was analysed by flow cytometry．The coculture of CD4+cells, antiCD3ε, antiCD28, IL12 and Sup ODN or control oligodeoxynucleotides(Con ODN) was performed for 72 hours,the nucleoprotein was extracted with regular  procedure. Expression of pSTAT4(phosphorylated STAT4)，pSTAT6，and Tbet in nucleoprotein were detected by Westernblot．ResultsCompared with Con ODN and PBS treated group, expression of Tbet and pSTAT4 in Sup ODN treated group decreased significantly (P<0.05), while expression of pSTAT6 in Sup ODN treated group increased significantly (P<0.05).ConclusionSup ODN may inhibit Th1 differentiation of mice CD4+T cell by downregulating expression of pSTAT4 and Tbet, and promote Th2 differentiation by upregulating expression of pSTAT6.