Regular spherical mesoporous bioactive glass microspheres (MBG-MSs) with tunable SiO2-CaO-P2O5 composition and adjustable mesoporous structure have been synthesized by a new approach of emulsification and solvent evaporation-induced self-assembly. Less ordered mesostructure and enhanced bioactivity resulting from the addition of CaO are investigated through scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction characterizations. The MBG-MSs have high storage capacities and sustained release patterns of anti-osteoporosis (alendronate sodium, NaAL) drugs which are hardly absorbed via oral administration. Furthermore, to some extent the dosage and release rate could also be controlled by CaO content. Cell viability and proliferation assay with rabbit bone marrow stromal cells indicates a positive effect of the CaO/P2O5 components on improving the cell growth cumulatively in about 2 weeks.