Objective. Recently our studies have shown that nylestriol in combination with levonorgestrel prevented bone loss, decreased bone turnover rate and increased the maximal loading of bone without obvious side effects in retinoic acid (RA) induced osteoporotic rats. In addition to the animal experiments, we evaluate the effect of Compound Nylestriol Tablet (CNT) on bone mineral density (BMD) in women with postmenopausal osteoporosis. Compound Nylestriol Tablet, which contains 0.5mg of nylestriol (cyclopentylethinyl estriol) and 0.15mg of levonorgestrel per tablet, was authorized as a new anti-osteoporotic agent for clinical trial in postmenopausal osteoporosis. Methods. One year's clinical observation was performed in 191 eligible patients who were randomly divided into two groups (A and B). In group A, 119 patients were treated for one year with CNT (one tablet per week) and in group B, 72 patients with placebo. Bone mineral density of lumbar antero-posterior spine (L1-L4), lateral spine, total hip and total forearm positions including radiustulna at the ultra distal areas, mid areas, and one-third areas, were measured before and after treatment. Biochemical parameters and effects of CNT on uterus, and breast were observed. Results. We found that patients treated with CNT had a significant decrease of bone loss in total forearm, including radiustulna at the ultra distal, mid, and 1=3 areas compared with control subjects (all P<0.05). An improved BMD tendency could be seen at the lumbar spine. There were no differences in the observed biochemical variables. No side-effects on uterus, or mammary glands were observed. None of the patients had uterine bleeding or vertebral fractures during one year's CNT treatment. Conclusion. These data suggested that CNT is effective, safe and convenient in treating postmenopausal osteoporosis.