In this study, Ce-O catalysts were prepared by the modified complexation method and their activities were tested for selective catalytic oxidation of H2S to elementel sulfur. The calcination process, which is the last step of catalyst synthesis, was performed at different temperatures (300 degrees C, 350 degrees C, 400 degrees C ve 450 degrees C) and the effect of calcination temperature on the catalytic activity was investigated. Activity tests with the synthesized catalysts were carried out in a fixed-bed reactor system using different feed ratios of O-2/H2S at 250 degrees C. The XRD patterns of all the catalysts, calcined at different temperatures, show the formation of cerianite phase with non-stoichiometric O-2 (CeO(2-x)) in the bulk phase. The XPS analysis of the Ce-O catalyst supported this result, while most of cerium was in +4 oxidation state, + 3 oxidation state was also observed in Ce-O catalyst. Rather high elemental sulfur selectivity (>= 97%) was achieved with all Ce-O catalysts. However, Ce-O-350 catalyst which was calcined at 350 degrees C gave the longest catalytic activity with an H2S conversion of 69% in selective oxidation of H2S. The decreasing of calcination temperature of the catalysts was resulted in the increase in its catalytic activity. Catalytic activity for longer periods which was achieved with Ce-O catalyst calcined at lower temperatures was due to better oxygen mobility of the catalyst.