Abstract: In order to investigate the effects of Pseudostellaria heterophylla fibrous root saponins（PHFRS） on immunomodulatory function in immunosuppressed mice, in the experiment, 80 male ICR mice were randomly divided into 5 groups, namely, blank control（CK） group, cyclophosphamide（CTX） group, and PHFRS low（L-PHFRS, 50 mg/kg）, medium（M-PHFRS, 100 mg/kg）, and high（H-PHFRS, 200 mg/kg） groups. On days 1 to 3, normal saline was injected into the CK group by intraperitoneal injection, and CTX（80 mg/kg by body weight） was injected intraperitoneally into all the remaining groups. On days 4 to 17, each PHFRS dosage group was fed with the corresponding dose of PHFRS, and the CK and CTX groups were given equal amount of purified water. On the 18 th day of sampling, the proliferation of spleen T and B lymphocytes was detected by MTT method and the stimulation index（SI） was calculated; serum immunoglobulins（IgA, IgM, IgG） and complements（C3, C4） were detected by immunoturbidimetric method; serum cytokine（IL-2, IL-4, IL-6, IFN-γ, TNF-α） were detected by ELISA method. The results showed that compared with the CK group, the T-lymphocyte SI and IgM content were significantly lower（P＜0.05） and the B-lymphocyte SI, IgA, C3, C4 and IL-4 contents were significantly higher（P＜0.05） in the CTX group; C3 content was significantly higher in the M-PHFRS group（P＜0.05）; C3, C4, and TNF-α contents were significantly increased in the H-PHFRS group（P＜0.05）. Within the three PHFRS concentration gradients, T-lymphocyte SI was dose-dependently increased, while B-lymphocyte SI showed no significant dose-dependence; serum immunoglobulins IgA, IgM, IgG and complements C3 and C4 levels were dose-dependently increased; among serum cytokines, except IL-6 showing dose-dependently increased level, IL-2, IL-4, TNF-α and IFN-γ levels showed different degrees of increase or decrease. The results indicated that PHFRS could promote the recovery of spleen lymphocyte proliferation function in immunosuppressed mice, and regulate the levels of immunoglobulins, complements and cytokines in serum, thus promoting the recovery of immune function in mice; in addition, the change of PHFRS dose had a certain degree of influence on the immunomodulatory effect.