Abstract: Objective To evaluate the effects of ibandronic acid sodium on bone mineral density (BMD) of prostate cancer patients with bone metastasis after androgen deprivation therapy. Methods Thirty cases of advanced prostate cancer patients were recruited in this study and received maximal androgen blockade therapy. Fifteen patients were randomized into the treatment group and received intravenous ibandronic acid sodium (4 mg, once a month, intravenous drip), and the other 15 patients were in the control group without ibandronic acid sodium treatment. There was no statistical difference in BMD index between two groups before androgen deprivation therapy. BMD of the lumber spine (L2-3) and the femoral neck were measured by dual-energy X-ray absorptiometry after 3, 6 and 12 months of treatment, respectively. Results After 3 months of treatment, BMD value was decreased in both group and there was no statistical difference(P>0.05). After 6 months, BMD was increased in the treatment group while decreased in the control group, and still with no statistical difference（P>0.05）. After 12 months, the difference in both groups was statistically different (P=0.001). Conclusion The BMD in prostate cancer patients was signifi cantly decreased after 12 months of androgen deprivation therapy, while ibandronic acid sodium could retard the decrease.