Hydrogen and deulerium have been introduced into palladuim cathods in an electrolysis process for 150 h with light and heavy water as electrolyte respectively. The palladuim cathods used had quenched or annealed after a thermal treatment at 950℃. The variation of diffraction pattern and lattice constant of β phase of palladuim-hydrogen system in air with time have been measured by X ray diffraction method. The distribution of hydrogen in the surface layer of palladuim-hydrogen system bas been measured by the nuclear reaction1H(19F,αγ)16O. Comparing a quenched palladuim cathod with annealed palladuim cathod, it is shown that the former has higher initial concentration of hydrogen and faster evolution velocity than the latter after the electrolysis. The concentration of hydrogen arrives its maximum at the surface of palladuim hydrogen system and its minimum at a depth of several hundred angstroms from the surface.