A biodegradable drug delivery system was established using an apatite cement containing simvastatin. The in-vitro drug release from apatite with lower-crystallinity was investigated under simulated osteoblast and osteoclast conditions (SOB and SOC). Apatite cement containing 6% simvastatin had lower crystallinity as the same as natural bone. In-vitro drug release tests were performed under SOB in simulated body fluid (pH 7.8), and then under SOC in acetate buffer (pH4.5) at 37.0｡C, and the process repeated twice. The device had lower drug release rates under SOB, but significantly higher rates under SOC. The simvastatin release rate was 15 times higher under SOC than SOB. The device showed dissolution medium responsive drug release. After implantation of the APC containing simvastatin in osteoporosis rats, the bone mineral density was evaluated by the X-ray computed tomography. The result indicated that the bone mineral density of APC implanted rat was significantly higher than that of control diseased.