The ^<29>Si and ^<31>P nuclear magnetic resonance (NMR) chemical shifts and the Q_n distribution in ternary sodium phosphosilicate glasses were examined. In the NaPO_3-SiO_2 glasses, only the Si(Q_4) unit from SiO_2 and the P(Q_2) unit from NaPO_3 are observed. When the P_2O_5 content increases at fixed mole fractions of SiO_2 equal to 0.1 and 0.05, the 6-coordinated silicon atoms appear. The presence of 6-coordinated silicon atoms is expected in glasses where the [P_2O_5]/[Na_2O] composition ratio is greater than unity. Their appearances can be understood in terms of the relative acidic st...