In this paper, we report the study on the poisoning of hydrogen storage material MlNi5 (Ml = La, Ce, Pr, Nd) by CO, O2, H2O using x-ray and ultra violet photoeletron Spectro-scopy (XPS and UPS), With increasing of the poisoning gas exposure, peak a (0.3eV) and peak b (1.2 eV) below EF in UPS show evident change, they decayed shift toward the higher BE side and form a shoulder gradually: While the peak c (6eV) and peak d (9.5 eV) shifted increase with gas exposure. The chemical states of poisoned material were identified by XPS technique.The MINi5 poisoned by oxygen was restcred by hydrogen at 300 ℃ and after regenerating we observed from UPS the increasing of a, b intensities.Similar results were obtained in MlNi5 material peisoned by carbon monoxide and water vapor and then heated in UHV and etched by Ar+.These results were further demonstrated by XPS. The experiment results provide information on the Charge-transfer between d-electron of transition metal nickel in MINi5 and free molecular orbital of poisoning gases. It is a base for understanding of poisoning and re-generating of surface catalysis in practical use.