Abstract: C57BL/6 mice were injected with B16 melanoma cells by eye's vein. After 24hours, these mice were irradiated with 75mGy X-ravs. The whole-body irradiation to mice caused a decrease of metastasis nudules in the lung. At the same time, the immune function in normal and tumor-bearing mice was also defected, it showed that immune function of irradiation group was enhanced than that of control group.