Abstract: The present study with weanling piglets rearing in common environment was conducted during an experimental period of 4 weeks to evaluate the effects of dietary supplementation with 50, 100, 200 mg/kg of β-1,3/1,6-glucan extracted from Saccharomyces cerevisiae on peripheral blood lymphocyte subgroups, lymphocyte proliferation and production of classical swine fever (CSF) antibody. Some humoral and cellular immune parameters were measured after 2 and 4 weeks.Lymphocyte proliferation of peripheral blood was determined indirectly by the MTT colorimetric assay method, peripheral blood lymphocyte subgroups were determined by Flow Cytometry using mouse-anti-pig monoclonal antibody, CSF antibody was determined by ELISA Test kit from IDEXX Inc. A total of 160 (Landrace×Large White) weanling piglets at (28±3)d of age were randomly allocated into four treatments according to initial bodyweight and gender, five replicates per treatment, 8 pigs per replicate (per pen). All pigs were vaccinated against CSF at 25 days of age. The results indicated that oral supplementation with β-1,3/1,6-glucan can significantly enchance lymphocyte proliferation of peripheral blood in weanling piglets after 14 days of administration (P＜0.01) but no significant effect was observed on d 28 (P＞0.05).We also observed that oral supplementation with β-1,3/1,6-glucan can enchance significantly CSF antibody titer on d 21 after inoculation(P＜0.05).In the present study, we also found that low dose β-1,3/1,6-glucan （50 mg/kg）has a numerical increase in Th cells, Tc cells, CD4+ T cells, CD8+ T cells and CD4+ /CD8+(P＞0.05), but high dose β-1,3/1,6-glucan （100 and 200 mg/kg）can significantly increase the number of CD8+ T cells (P < 0.05), significantly decrease CD4+ /CD8+(P＜0.05). Based on above results, we concluded that oral supplementation with β-1,3/1,6-glucan might have a transient and slight influence on immune function of weanling piglets, might be used as immune adjuvant but its actions were influenced by the dose level and times of administration. Low dose and short term of β-1,3/1,6-glucan supplemenation are beneficial to immune but high dose or long period supplemenation might lead to immune maladjustment.