This article is a brief summary of our study on poisoning and regenerating at the surface of LaNi5 by impurities, which are H2S, SO2 and CS2 contained in the hydrogen used. The AES, XPS analysises show that the feature of the poisoning for three sulfides are different: LaNi5 poisoned by H2S produces the surface compounds, such as La2S3 and NiS. The chemisorption and physisorption occured due to SO2 and CS2 poisoning respectively.In addition, surface catalystic property of active nickel on LaNi5 can be shown by evalution of the changes in the intensity of nickel peak in the Ni(2p3/2) spectrum. Pure hydrogen cycle method is effective for regeneration of LaNi5 poisoned by SO2 and CS2, but this is not true for H2S-poisoned samples. These results are very useful in explaining the mechanisms of rare earth intermetallic hydrides surface poisoning and regenerating.