Objective To study the effects of Pseudognaphalium affine D.Don Anderberg（PADA）on reproductive hormone levels and immune function in rats.Methods PADA was extracted and concentrated according to the traditional eating habit， and given orally to SD rats for 30 consecutive days. Six sex hormones， immune organs， carbon clearance assay， ConA-induced splenic lymphocyte transformation test， determination of serum hemolysin and determination of antibody producing cell were measured.Results The prolactin levels was elevated （P<0.05） in female rats of all dose groups after exposure to PADA. Spleen weight in the male 100 g/kg.bw dose group， antibody product in the male 50 g/kg·bw dose group and thymus weight and thymus-body ratio in the female 100 g/kg·bw dose group were increased （P<0.05）. While no significant adverse changes were observed in the phagocytic index-a， the OD difference value of lymphocyte transformation test， Hemolytic plaques， WBC， globulin， the albumin/globulin ratio， and immune organs.Conclusion Prolactin levels can be increased in females at doses above 25 g/kg·bw. No significant impairment of immune function was observed. Spleen weight， thymus weigh， and thymus-body ratio were increased， suggesting a certain immune enhancement effect.