Objective To study the effects of Lactobacillus acidophilus（L.acidophilus） on the proliferation and cell cycle distribution of human tongue cancer cells（Tca8113 cells）. Methods In vitro cultivated human Tca8113 cells were treated by L.acidophilus supernatant, inactivated bacilli, cell free extracts and normal culture medium respectively, which were 1, 4, 16-fold（s） dilutelly, to investigate the proliferous effects of Tca8113 cells using of inverted microscope, cell counting, sulforhodamine B（SRB） and flow cytometry. The free radicals and Ca2+ in Tca8113 cells were also studied by confocal laser scanning microscope（CLSM）. Results At the 48th hour after adding different L. acidophilus components, the Tca8113 cells changed in shape from the diamond-like, polygonal and slabs into the elongated form. In the condition of different times and different culture concentrations, the proliferation of Tca8113 cells was significantly inhibited by L.acidophilus components, which enhanced as the time prolonged and the concentrations of each L. acidophilus components increased according to the cell counting and the SRB experimental analysis. The cell proliferation index（CPI） was significantly reduced（P
