Local structure around oxygen is directly elucidated by 17O nuclear magnetic resonance (NMR). However, the 17O NMR spectra in borosilicate glasses are quite complicated, and hence the assignments of the peaks have been empirically done. In the present study, 17O NMR parameters for the various oxygen sites in the borosilicate system were obtained from the ab-initio molecular orbital calculations using the Gaussian03 programs. As for the oxygen atoms in SiOSi, SiOB, and BOB bridging bonds (B[n]: n-fold coordinated boron), the isotropic chemical shift δiO decreased with increasing the bond angle. The oxygen atoms coordinated by B as SiOB, BOB, and BOB bridges showed weak dependency in δiO against the bond angle, and BOB showed a maximum in δiO at 150°. The quadrupole coupling constant Cq of all the bridging oxygens increased with increasing the bond angle. When the oxygen atoms in SiOB, BOB bridges were coordinated by Na ion, δi O decreased by 5 ∼ 10 ppm. The oxygen atoms in trimeric ring clusters showed different δiO from dimeric clusters, indicating that δiO was also influenced by the second neighboring cations. The order of δiO was expected as SiOSi < SiOB < SiOB < BOB < BOB < BOB, which was in accordance with the order of bond covalency.