As far as the authors' knew, there was few report on the effects of antibacterial peptide on the cellular immunity in weaned piglets.The aim of this study was to evaluate the effects of dietary supplementation of antibacterial peptide (ABP) and astragalus polysaccharide (AP) on T lymphocyte cells proliferation,T cell subset of peripheral blood, lymphocyte cycle, and apoptosis of spleen in weaned piglets.A total of 90 piglets (Duroc × Landrace × Yorkshire) were randomly allotted to five groups, including the control group, the antibacterial peptide groups containing 250,500 and 1 000 mg/kg antibacterial peptide,respectively, and the astragalus polysaccharide group with 400 mg/kg astragalus polysaccharide.The whole experimental period was 28 days.Six piglets in each treatment group were selected randomly for obtaining blood samples from the jugular vein for T lymphocyte cells proliferation and subpopulation analysis at 32,39,46 and 53 days of age.Six piglets were selected from each treatment group and euthanized for cell cycle and apoptosis of spleen at 39 and 53 days of age.Supplementation with ABP increased (P <0.01) the Go/G1 phase in the cycle of spleen, and decreased (P < 0.01) the S phases, the G2 + M phases and the PI in the cycle of spleen.The percentages of apoptotic spleen ceils were significantly decreased (P <0.01).Supple-mental ABP increased the value of lymphocyte proliferation (P <0.01).The percentage of CD3 + , CD3 + CD4 + , CD3 + CD8 + and CD4 + CD8 + ratio of AP group and ABP groups were increased (P < 0.05 or 0.01).In conclusion, the results showed that ABP intake could improve the T-cell proliferation, the relative proportion of the subsets of T-cells, and the cycle of spleen cells, and decreased percentage of apoptotic cells.The cellular immune function was finally improved in weaned piglets.The optimum add dosages were found to be 500 mg/kg for 4-week adding and 1 000 mg/kg for 2-week adding, individually.