Abstract: The reaction of T lymphocytes to ConA was suppressed after mice were irradiated by UVC in the dosage of I36mJ/cm². However, the reaction of T lymphocytes to ConA didn’t change significantly following UVC radiation of 1085mJ/cm². The suppression was signicant 12 hours after UVC rediation and returned to normal level 36 hours after UVC radiation. The effect of UVC radiation at dosage of 136mJ/cm² on IL-2 activity and spontaneous proliferation of thymocytes was significant.