Persistent spectral hole-burning spectroscopy has been carried out for the 3 H 4 → 1 D 2 transition of Pr 3+ in (100− x)SiO 2· xNa 2O glasses with x=10, 20, 33.3 and 45 in order to examine the effect of Na 2O content on the homogeneous width and hole-burning efficiency. The homogeneous width shows a nearly T-linear dependence below about 10 K irrespective of glass composition, which is characteristic of optical dephasing due to dynamical process associated with low-energy excitation modes in glasses. Both the homogeneous width and hole-burning efficiency increase with an increase in Na 2O content at 4.2 K. These observations are interpreted based on the coupling of the 3H 4– 1D 2 transition of Pr 3+ to the low-energy excitation modes in sodium silicate glasses.