Abstract: Three different tumor cell lines' apoptosis induced by 188Re radiation is detected by MTT assay, light microscope, transmissional, electron microscope and flow cytometer, and the expression of Bcl-2 protein and Bax protein during the apoptosis are detected by image method. The results indicate that the three kinds of tumor cell lines can be killed by 188Re radiation with dose-effect relationship. With rise of radiation dose and prolongation of culture time, the tumor cell apoptosis rate is increased, the expression of Bcl-2 is decreased, and that of Bax enhanced, which causing the ratio is reduced. The cells are arrested in G2/M phase; the three kinds of cell are very different in sensitivity to 188Re radiation from PC-3 cell higher to A549 cell lower.