Abstract: Objective To observe the expression of Bcl-2 and its phosphorylation in Molt-4 cells induced by tumor necrosis factor-α (TNF-α),and to investigate the possible mechanism of cell cycle specificity of apoptosis. Methods Exponentially growing Molt-4 cells were treated with TNF-α.Apoptosis was detected by DNA fragmentation assay.API Method was applied to illustrate the cell cycle specificity of apoptotic cells.Cells of sub-phases were sorted by FACSvantage flow cytometer and then submitted to immunoblot. Results Molt-4 cells which were treated with TNF-α went to apoptosis and showed a DNA ladder pattern.Most apoptosis happened in G1-phase of cell cycle.Bcl-2 expression increased for the Molt-4 cells treated with TNF-α.The phosphorylation state of Bcl-2 was only presented in G1-phase cells,in accordance with the specified time and cell cycle phase of apoptosis. Conclusion The phosphorylation of Bcl-2 in the Molt-4 cells treated with TNF-α happened with the same cell cycle specificity as cell apoptosis.The cell cycle specificity of Bcl-2 phosphoryaltion was one of the mechanisms of receptor-mediated apoptosis.The cell cycle machine can trigger the apoptosis program.