The biomaterials in system CaO-P2O5-SiO2 were synthesized via sol-gel method. The biomaterials can be applied to bone reparation and bone tissue engineering scaffolds The nano-pore structure, degradability, bioactivity and bio-mineralization characteristic of the biomaterials were investigated in details using XRD, SEM/EDX, FTIR, BET and DSC/TG techniques. It was indicated that the sol-gel derived biomaterials have a higher bioactivity than that of the melt derived bioactive glasses or glass-ceramics. It just takes 4-8 hours for HCA to form on the surface of the sol-gel samples in SBF solution at 37°C. The spherical HCA crystal clusters formed on the surface of the sol-gel derived samples immersed in SBF for 8 hours have a low crystallinity. Owing to their interconnected nano-sized pores, the sol-gel samples possess much higher surface areas and the hydrous porous SiO2 gel layer containing a great amount of ºSi-OH groups can be rapidly formed on the biomterials’ surface through a quick ion exchange between H3O+ in the solution and Ca2+ in the surface of the materials. ºSi-OH groups can play a very important role in inducing formation of HCA. They make the material surfaces electronegative, which resulted in a double electrode layer formed between the samples surface and SBF solution. The double electrode layer is in favor of formation of HCA on the surface of the materials.