Objectives:To investigate the biological effects of 125I seeds compared with 60Co radiation on non-small cell lung cancer (NSCLC) cells A549 and normal bronchial mucosa epithelial cells BEAS-2B. Materials and Methods:A549 and BEAS-2B cells were exposed to 125I seeds radiation and 60Co radiation, respectively. The experimental groups were exposed to 125I seeds radiation and 60Co radiation at 2, 4, 6 and 8Gy, control groups were subjected to the same procedure without radiation (0Gy). The survival fraction, cell apoptosis, cell cycle, and the expression of apoptosis related proteins were detected, respectively. Results:The surviving fraction of A549 and BEAS-2B cells induced by 125I seeds radiation and 60Co radiation were significantly decreased compared with control group. And the surviving fraction induced by 125I seeds radiation was significantly lower than that of 60Co radiation. A G1 arrest in A549 cell was observed after irradiation with 125I seeds at 4, 6 and 8Gy. Both 125I seeds radiation and 60Co radiation led to a markedly increase of apoptotic cells at 4, 6 and 8Gy on A549 cells. 125I seeds radiation led to a higher percentage of apoptotic cells than that of 60Co radiation. Both 125I seeds radiation and 60Co radiation significant upregulated the expression of Bax protein and down-regulated the expression of Bcl-2 protein at 4 and 8Gy on A549 cells, moreover the effects induced by 125I seeds radiation were more obvious than that of 60Co radiation. The apoptotic ratio and the expression of apoptosis-ralated protein in BEAS-2B cells had little difference between two types of radiation. Conclusions:Both 125I seeds radiation and 60Co radiation led to a remarkable growth inhibition and apoptosis promotion on NSCLC cells, 125I seeds radiation was more prominent compared with 60Co radiation. The imbalance of Bcl-2/Bax and the activation of Caspase-3、PARP proteins may play an important role in the antiproliferative effect induced by 125I seeds radiation.