Abstract: In this paper the X-ray Photoeleotron Spectroscopy (XPS) analysis on the LiNbO₃ waveguide samples is reported. The samples were prepared by ion migration enhanced by electric field. The elements such as Ag, Tl, Nb and O in the different mode number waveguide planes on both the positive and the negative sides were measured. The depth profile of Ag and Tl ions in the waveguide layer was analysed. The results show that the Nb⁺⁵ in the LiNbO₃ samples prepared by this method has no change of valency. The concentration of Ag⁺ on the positive guide side increases with the salt-bath time, but there isn't similar rule on the negative guide. The results of depth profile analysis show that the migration depth of Ag+ and Tl+ ions is about 500~2500Å. The ion distribution in the positive guide layer presents a step, then decreases as a complementary error function. Whereas the ion distribution in the negative guide layer is a complementary error function. Compared with the calculated results of optical measurement, the migration depth of the Ag⁺ and Tl⁺ ions is less than the 1/10 depth of the waveguide layer.