The low crystalline hydroxyl carbonate apatite forming capacity of a poly (70lactic-co-30glycolic acid)/15CaO-85SiO2 composite, which had a dual pore structure, was newly examined in simulated body fluid. The bioactive 15CaO-85SiO2 particles were synthesized by a sol-gel method using tetraethyl orthosilicate (TEOS) and calcium nitrate tetrahydrate under acidic condition followed by the heat treatment at 600°C for 3h. The poly (70lactic-co-30glycolic acid)/15CaO-85SiO2 composite was then prepared by a solvent casting using dimethylformide as a solvent. The composite was loaded into a high pressure chamber and then carbon dioxide gas was introduced achieving a final pressure of 20 MPa. After 3 days, carbon dioxide gas was released quickly and resultantly the dual pore structure was obtained. The samples were observed by FE-SEM and its bioactivity was tested in simulated body fluid.