In order to investigate the effects of human anti-proliferative protein Tob1 (transducer of ErbB2,1) on the radio-sensitivity of human cervix cancer cells HeLa, the full length Tob1 recombinant plasmid pcDNA3.0/Tob1 (pc3/Tob1) was constructed and transfected into HeLa cells by lipofectamine. And G418 selection was used to get HeLa cell line stably expressed exogenous Tob1. The clonogenic assay was applied to study the effects of Tob1 on HeLa cell radio-sensitivity, while flow cytometry assay and Western Blot analysis were performed to determine the related mechanisms. It was shown that, compared with parental HeLa cells and mock plasmid pcDNA3.0 transfected HeLa/pc3, the radio-sensitivity of HeLa cells transfected with Tob1 was increased obviously. It was also found that increased Tob1 expression could enhance cell apoptosis of HeLa induced by irradiation, while up-regulated protein expression level of Bax, but down-regulated Bcl2 expression occur at the same time. These results suggested that Tob1 might play a role as radio-sensitizer of cervix cancer cell line HeLa via regulating the expression of apoptosis related genes.