Dielectric behavior and optical absorption of quartz glasses before and after irradiating were investigated. Experimental results demonstrate that complex dielectric function of quartz glasses is changed by the irradiation. Its magnitude is decreased by the irradiation. In addition, the change in the dielectric function does not relate to the hydroxyl group in quartz glasses. Experiments also show that dielectric function is relating to the color centers in quartz glasses. Contribution of color center to dielectric function is dependent on its sort and amount in quartz glasses. Dielectric constant decreases with increasing the density of color center