This paper reports the effect of total body irradiation with low dose radiation (LDR) on tumor inhibition and the dynamic changes of immunological indexes in Lewis lung cancer cell-inoculated mice in 20 days. Results show that tumor inhibitory rates in single and fractionated irradiation of 75mGy were 40% and 51% respectively, splenic NK cell activity was elevated in 1 to 4 days, CD4 and CD8 levels on T lymphocyte surface were up-regulated early to some extent, and the ratio of CD4/CD8 was risen post-irradiation. It suggests that under the experimental condition LDR might lead to growth inhibition of Lewis lung cancer cells and immunological hormesis in the tumor-bearing mice.