The structure of xCaO center dot(100 -x)P2O5 glass system with 25x40mol.% was investigated by means of Raman and infrared spectroscopy. The characteristic bands due to the stretching and bending vibrations were identified and analyzed by the increase of CaO content. The structural changes induced by the CaO presence in phosphatic matrix were determined and discussed in terms of the network depolymerization process and distortion of the PO4 tetrahedra.