The change mechanism of optical constants of glasses under the action of thermal, stress, acoustic and electric fields is analysed on the basis of the dispersion theory. The change rules of temperature coefficient of refractive index, photo-elastic constant, stress-optic constant, thermo-optic constant and nonlinear refractive index of glasses and the relationship between these properties and chemical composition and structure of glasses are presented. The calculating methods of above properties have been developed by present work. The intense laser induced thermal blooming, self-focusing and damage in glass are discussed in terms of nonlinear change of refractive index of glasses.