Abstract: Objective:To investigate the effect of Naja Naja Actra Venom Component (NNAVC) on the proliferation and cell cycle of KG1a cells.Methods:The human acute myeloid leukemia (AML) cell KG 1a was chosen as the experimental subject. After exposure to different concentrations of NNAVC, MTT assay was used to detect the inhibitory action of NNAVC on KG1a cells. Morphological changes of KG 1a cells were observed by inverted microscope before and after administration of NNAVC. Cell cycles were measured via flow cytometry.Results: NNAVC obviously inhibited the proliferation of KG 1a cells. The results suggest NNAVC inhibited the KG 1a cells in a time- and dose-dependent manner within the range of ( 0.7 -1.2) μ g/mL. Smal ler volume, deformation, vacuole wi thin the cel l , cel l pyknosis and other morphological changes were gradually observed by inverted microscope after6 hours. After treatment with NNAVC, flow cytometry analy-sis showed KG 1a cells were arrested in G0 /G1 stage and significantly decreased in G2/M stage. Conclusion:NNAVC can obviously inhibit the proliferation of KG1a cells. KG 1a cells were arrested in G 0 /G1 stage and significantly decreased in G2/M stage. This data suggests the change of cell cycle progression may be one of the underlying mechanisms of NNAVC inhibit-ing the growth of KG1a cells.