A rat model of lack of estradiol ( E2 ) was established by X-ray irradiation to ovaries. It was found that the reduction of E2 level in serum, increase of interleukin 2 ( IL-2 ) secretion and hyperplasia of lymphocytes. There was also a negative correlation between the level of E2 in serum and IL-2 production(r= -0.952, P<0.0005). The model would be a good subject for the associated research between estrogen and immune system.