To enhance the potency, reduce the side effects and improve oral property of estradiol in estrogen replacement therapy (ERT), 6 novel estradiol–RGD octapeptide conjugates have been prepared. In an ovariectomized mouse osteoporotic model, at an oral dosage of 110.3 nmol/kg per day, their anti-osteoporosis activity was significantly higher than that of estradiol and estradiol–RGD tetrapeptide conjugates