The mineralization process of calcium carbonate (CaCO_3) in vivo was mediated by organic matrix. The research progress on the biomineralization of CaCO_3 in vitro mediated by organic matrix and synthetic organic compounds was reviewed in this paper. Organic matrix provides the template of nucleation and growth of CaCO_3, and mediates the crystallographic orientation, polymorph and morphology of CaCO_3. It gives these CaCO_3 crystals special physical and chemical properties. On the other hand, CaCO_3 crystals also influence the microstructure of organic matrix.