Estrogen is a factor supporting the equilibrium of bone metabolism and inhibiting the immunological function of lymphocytes. In this paper, the occlusion of ovarian follicle, the reduction of estrodiol secretion, the increase of values of Ca/cr and HOP/cr in urine and ALP in serum, the decrease of MTN (mean trabeculae number) and MTV, (mean trabeculae volume) and the increase of proliferation and secretion of IL-2 in splenic of rats wese observed when their ovaries had been irradiation with X-rays of 50Gy. There was obviouse negative correlation between the IL-2 secretion and the level of estrodiol in serum. It also showed marked positive correlation between the level of calcium in urine and the activity of IL-2 secreted by splenic lymphocytes. It was suggested that the bone metabolism and the immunological function of lymphocytes could be influenced by the ovaries exposed to irradiation. The effect of estrogen on bone metabolism might be mediated by IL-2.