Abstract: To induce cell apoptosis with ionizing radiation becomes an important method in treating tumor now. The correlation between cell apoptosis (a kind of active cell death)and the inducing of ionizing radiation becomes more and more specific. The character of cell apoptosis in-duced by ionizing radiation is related with cell membrane's change. Cell apoptosis is related with radiation dose, radiation way and linear energy transfer (LET). The mechanism of cell apoptosis may include gene control, signal transduction, ion metabolizability, enzyme and protein. All of these make a complicated biological network.