Objective To investigate the influence of Ginkgo biloba endocarp polysaccharide (GBEP) on the immune function of normal Balb/C mice. Methods Low, middle or high dosage of GBEP and distilled water were administered intragastrically to four groups of mice respectively for 30 days. The effects of GBEP on immunological indices of mice were observed． Results The percentage of T lymphocytes, Th lymphocytes and the ratio of Th/Ts in peripheral blood were significantly higher in GBEP groups than those in the control group (P<0.05). There were no significant difference of other immunological indices between the control group and GBEP groups. Conclusion There were certain modulation of GBEP on immune functions of normal mice under the dosage in this study.