UV-visible absorption spectra for the bulk lead silicate glass with different lead concentrations (mole fraction of PbO change from 0.30 to 0.50) were measured before and after irradiation with the frequency-quadrupled output of a Q -switched YAG laser (266 nm,10 Hz repetition rate). Different UV-visible spectra changes were observed after exposure to laser beam with different energy density. Exposed to the 266 nm laser beam with high energy density (150 mJ/cm 2), a visible brown spot could be seen on the surface of the exposed region, and the absorption coefficient increases evidently in wavelength range measured. Exposed tot he 266 nm laser beam with low energy density (50 mJ/cm2), no visible spot was observed, but the absorption spectra showed that the absorption coefficient increased slightly over the wavelength range observed, and the refractive index decreased evidently. The largest refractive index change Δn is -0.25. Irradiating a sample with different energy density, the absorption coefficients in visible wavelength increased suddenly when the energy density was larger than a threshold value. This may be caused by the structural changes of lead silicate glasses induced by the increasing of the temperature in local region of the lead silicate glass.