Pure bredigite (Ca7MgSi4O16) powders are synthesized by the sol-gel method. The bredigite powders are composed of polycrystalline particles with dimensions of 1-10 micro m. The in vitro bioactivity of the bredigite powders are examined by evaluation of hydroxyapatite (HAp) formation ability in simulated body fluid (SBF) and the effect of ionic products from bredigite dissolution on osteoblast proliferation. The results showed that bredigite induced the formation of nanocrystalline HAp after soaking in SBF for 10 days. The Ca, Si, and Mg ions from bredigite dissolution at a certain concentration range stimulates osteoblast proliferation. Our study indicates that bredigite is bioactive and might be used for preparation of new biomaterials.