The present study was designed to evaluate the effects of Prunella Vulgaris (P. vulgaris) on the immune function in mice. The mice were randomly divided into one control group and three treatment groups of 10 mice each. The control group received pure water and the treatment groups received P. vulgaris extract at concentrations of 0.15, 0.30 and 0.90 g/kg BW orally for 30 days, respectively. Changes in cell immune function, non-specific immunity and humoral immunity function were evaluated. Active lymphocytes and T lymphocyte subsets were determined by fluorescence-activated cell sorting (FACS). Certain Serum concentrations of cytokines were measured by enzyme-linked immunosorbent assay (ELISA). The results showed that, for cell immune function, compared with the control group, foot pad thickness in high dose group increased significantly (p<0.01), whereas no significant difference in the proliferative ability of splenic lymphocytes was observed among all groups (p>0.05). For non-specific immunity, NK cell activity increased significantly in a dose-dependent manner in P. vulgaris treated mice (p<0.01), mononuclear-macrophage function in medium and high dose P. vulgaris treated mice were significantly higher than that of the control group (p<0.05). For humoral immunity, no significant differences were observed in terms of the half value of hemolysis (HC50), number of hemolytic plaques and serum IgG level (p>0.05). The percentage of active T and Th lymphocytes of mice peripheral blood in high dose group were significantly higher than that of the control group (p<0.01). There was no significant difference in serum levels of IL-1β, IL-4, IL-10 and IFN-γ among all of the four groups (p>0.05). The data indicated that 0.90 g/kg BW P. vulgaris extract (equivalent to 7.5 g/kg BW crude drug) had some effect on cellular immune function and non-specific immune function in mice.