We have studied the structural and chemical changes of Rh on Al₂O₃/NiAl(100) depending upon heat treatment, and the oxidation reaction of atomic sulfur on Rh/Al₂O₃/NiAl(100) surface under atmospheric environment by means of Near Edge X-ray Absorption Fine Structure, X-ray Photoelectron Spectroscopy and Atomic Force Microscopy techniques. Rh nanoclusters are formed on the Al₂O₃/NiAl(100) surface after the deposition of Rh. With elevated temperature, the aggregation of Rh atoms occurs on the Al₂O₃ layer at 600 K. At the temperature range from 600 to 1000 K, Rh atoms diffuse and dissolve into the NiAl(100) substrate through Al₂O₃ layer. On the other hand, the S 2p XPS and S K-edge NEXAFS studies indicates the noticeable oxidation of the atomic sulfur adsorbed on Rh/Al₂O₃/NiAl(100) under atmospheric environment. In this oxidation reaction, not only the reaction temperature but also the degree of O₂ partial pressure seems to be important. [DOI: 10.1380/ejssnt.2009.65]