Abstract: Aiming to research on the brain tumors irradiation sensitivity, the cell proliferation, apoptosis and cell cycle in the SH-SY5Y cell line following irradiation were measured. At different doses, SH-SY5Y cells damage were assessed by cell counting, PI staining and caspase 3/7 and caspase 8 activity. The cells damage is distinctive between 5 GY and 10 GY or 20 GY, and the high dose irradiation induces the cells number decreased and the apoptosis protein caspase 8 and caspase 3/7 activity increased. These results reveal the cell happen to be apoptosis and cell cycle arrest. The γ-ray irradiation results in cell cycle arrest and cell apoptosis, and cell damage level is associated with the irradiation dose. Although the cell cycle arrest inhibited apoptosis, the high dose still induces the cell apoptosis protein activity increased in cell cycle arrest process. Cycle arrest is proved to be very important in the radioprotective mechanism of SH-SY5Y cells.