Abstract: 2-3-Estrone-N-ethyl-piperazine-methyltetracycline (XW630) showing anti-osteoporosis activity is a new compound with piperazine-tetracycline in the steroid structure of estrone. The affinity of XW630 with uterine estrogen receptor and its estrogenic activity were studied in this paper. The relative affinities of estrone, estradiol and XW630 with estrogen receptor (ER) of the uterine myoma tissues were found to be 0.325,1.000 and 0.011, respectively, by the competitive assay. The estrogenic activity index of estrone, estradiol and XW630 were shown to be 9.70,10.30 and 6.90, respctively, by the uterine weight assay using immature mice. These indexes indicate that: the estrogenic activity of XW630 is about 11960 that of estrone and 17742 that of estradiol. The vaginal smear assay of oophorectomized mice also showed that the estrogenic activity of XW630 is less than that of estrone and estradiol.