Abstract: OBJECTIVE To compare the differences of mouse thymus atrophy models induced by different administration times of estradiol benzoate(herein after reffered to as "estradiol"). METHODS Forty-four mice were divided into 4 groups on average. Estradiol benzoate injection (0.1 mg each) was injected every other day, in which estradiol A group was injected 3 times, estradiol B group was injected 6 times, and estradiol C group was injected 9 times. The control group did not perform any experimental operation. The thymus and spleen index, blood index, pathological changes of thymus, apoptosis of thymic cells and expression of related proteins were measured 24 h after the last administration. RESULTS The thymus index of mice in estradiol A and B group was significantly reduced compared with control group(P<0.01). In the blood cell analysis results, the white blood cell count of the estradiol B group was higher than that of the control group(P<0.05), and the percentage of lymphocytes of the A and B groups was lower than the control group(P<0.01). The content of MDA in the plasma of estradiol B and C group was significantly increased compared with control group(P<0.01), and the content of GST in the plasma of estradiol A group was higher than that in the control group(P<0.05). The results of HE staining and TUNEL apoptotic examination showed that the thymus lesions in the estradiol B group were the most severe, and the cells had a large number of apoptosis, while the estradiol C group was close to the control group. The thymus apoptosis and inflammatory protein(caspase-3, NF-κB) activation in the estradiol B group were much higher than those in the other groups(P<0.01). CONCLUSION The estradiol model group with 3 and 6 administration times are more successful, and increasing the times of modeling can't maintain the model state.