Abstract: Objective: To investigate the changes of the cell cycle of differentiated HL-60 initiated by dimethylsulphoxide(DMSO) and explore the specific phase of the cell differentiation in cell cycle.Methods: HL-60 cells influenced by dimethylsulphoxide capable of inducing differentiation for different time were used as subjects.The cell volume and the differentiation marker on the cell surface were analyzed by flow cytometry.The differentiated cells were identified by confocal microscope after stained with propidium iodide.Meanwhile,The change of the cell cycles induced by those drugs was analyzed by flow cytometry.The expression level of Ki67 in G₁ phase was tested by flow cytometry.The specific phase of the drug-induced cell differentiation in cell cycle was explored by flow cytometry sorting combined with confocal microscopic pictures of the different phase cells.Results: When the drug-induced time prolonged,the induced cell volume enlarged and the induced cells began to express CD11b(differentiation marker of myeloid cell).The peak value of G₀/G₁ phase was elevated in drug-induced cell cell cycle and the level of S phase was declined in drug-induced cell cycle.The expression level of Ki67 in G₁ phase was gradually declined.The differentiated cells were only observed in G₀/G₁ phase.Conclusions: Dimethylsulphoxide can induce HL-60 cell to differentiate along the way to granulocytic cells and induce the arrest of cell cycle in early G₁ phase to late G₁ phase.The cell differentiation was completed in early G₁ phase in cell cycle.