Purpose: In order to understand the mechanism of the stimulation effects of low dose radiation (LDR) , we observed the immune changes of T-lymphocyte subsets. Meteria and methods: Whole body of BALB/C bring-tumor mice were exposed to the doses of 5, 10,20 and 50cGy γ-rays. The changes of T-lymphocyte subsets in peripheral blood, spleen and tumor-infiltrating lymphocyte (TIL) were studied with flow cytometry (FCM) . Results: The ratio of ,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42489940&type=,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42489959&type=,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42489950&type=, remarkably increased in the peripheral blood and spleen (p,<,0.01) and the ratio of ,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42489953&type=,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42489955&type=,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42489954&type=, further decread in the TIL group of mice exposed 10cGy (,p,<,0.05) . Conclution: We suggested that the immune functions were promoted by the stimulating effects of LDR of γ-rays in the bodies of the bring-tumor mice. CTL, expressing ,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42489956&type=,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42489973&type=,http://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=42489957&type=, molecules, were concentrated in the tumor tissues and they carried out the killing function to the tumor cells.