Abstract: The protective effect of DNA on the cell membrane damage induced by ultra-violet radiation was studied. Rat erythrocytes were used as experimental materials. Blood samples were taken from the rat, and centrifuged to separate the plasma. The cells were washed twice with isotonic saline, resuspended in noraml saline solution and then irradiated by ultra-violet radiation. The DNA was added before or after irradiation. The cell suspensions were kept at 5℃ for 20 hours after irradiation, and then centrifuged. The supernatants were used for hemoglobin determination. The main results obtained may be summarized as follows, the cell suspension of erythrocytes were irradiated for 5, 10 and 20min. The amount of hemolysis induced by irradiation dosage revealed a direct proportional relationship. If DNA (20-40μg/ml)was applied before irradiation, the amount of hemolysis induced apparently decreased. The differences between the control and DNA treated were statistically significant, P<0.01, but insignificant for DNA added after irradiation.