Abstract: To observe the effect of Panax notoginseng lyophilized powder and Panax notoginseng saponins(PNS)on the differentiation of mouse CD4⁺T cells into Th1 cells,and to explore the potential mechanism of Panax notoginseng as a drug-synonym for improving immunity. Methods:Splenocytes from C57BL/6 mouse were selected and CD4⁺T cells were sorted for culture. Cells were divided into control group,Panax notoginseng lyophilized powder groups(160,320,640 μg/mL)and PNS groups(5,10,20 μg/mL),and cultured for 48 hours. The optimal concentration of Panax notoginseng lyophilized powder and PNS was screened by CCK-8 method. Effect of IFN-γ in supernatant was detected by enzyme-linked immunosorbent assay(ELISA). Relative expression levels of IFN-γ mRNA and T-bet mRNA were detected by q-PCR. Results:Compared with the control group,the expression level of IFN-γ,IFN-γ mRNA and T-bet mRNA in the Panax notoginseng lyophilized powder groups and PNS groups were significantly lower than control group(P<0.05). Conclusion:Panax notoginseng lyophilized powder and PNS could inhibit the differentiation and activity of Th1 cells.