Abstract: The diffusion coefficient D of hydrogen in TiNi alloys was determination with electrochemical method at 20±0.3℃. The value of D was (6.45±0.78)×10~(-7) cm~2·s~(-1). (fig.1,2). The activity energy of hydrogen diffusion in TiNi alloy was. 16.59 kJ·mol~(-1) (fig.3). The data of X-ray protolelctron spectroscopy (XPS), auger electron spectroscopy (AES), scan electron microscop (SEM) and energy dispersive analysis of X-ray (EDAX) showed that after charged-discharged hydrogen several cycls by electrochemical method, a layer of titanium oxide which contains no nickel was coated on surface of TiNi alloy electrode, beneath this oxide layer there was a Nickel-rich alloy layer, in which the ratio of titanium to nickel is 1:1.28. Thus we concluded that there is a layer of Nickel metal beneath the oxide coating surface. This results coincide with the conclusion of van waldkirch~[15].