To study the adjuvant effect of Radix Pseudostellariae fibrous roots Saponin (RPFRS) on mice immunized with Ovalbumin (OVA).60 ICR female mice were randomized into control group (CK group),individual immunization OVA group (OVA group),RPFRS low,medium and high dose groups (50,100,200 mg/kg) (D,Z,G groups).On day 1st-5th,16th-20th of the experiment,the other groups were given the corresponding dose of RPFRS except CK and OVA group.On the 6th and 21st day,except for the CK group,0.2 mL of PBS was injected subcutaneously,and 0.2 mL of OVA solution dissolved in PBS was injected into the other groups,that is,the injection weight of OVA in the other groups was 100 μg,twice in total.During the period,each group was free to eat and drink.On the 36th day,related indicators were tested.The results showed that compared with OVA group,the RPFRS groups significantly raised the stimulation index of T cells and OVA(P<0.05).The stimulation index of B cells in D group was significantly increased (P<0.05),the contents of IL-2 and IL-4 in group D and G were significantly increased (P<0.05),and the contents of IFN-γ in group G was significantly increased (P<0.05).The contents of OVA-IgG and OVA-IgG1 in RPFRS groups were significantly increased (P<0.05),the contents of OVA-IgG2a in group D and G were significantly increased (P<0.05),the contents of OVA-IgG2b in group D and Z were significantly increased (P<0.05).The relative expression of IL-2 mRNA,IL-4 mRNA and IFN-γ mRNA in RPFRS groups were significantly increased (P<0.05),and the relative expression of IL-10 mRNA in G group were significantly increased (P<0.05).The number of CD3⁺, CD8⁺ T cells and the ratio of CD4⁺/CD8⁺ in RPFRS groups were significantly increased (P<0.05),and the promoting effect on CD4⁺ T cells was the most obvious in group D and Z (P<0.05). In summary,RPFRS can enhance the immune function of mice,improve the immunogenicity of OVA and enhance the immune response ability of mice to OVA,thus playing a certain role as an adjuvant.