Thermal efficiencies of an integrated gasification combined cycle (IGCC) process can be enhanced with high-temperature desulfurization. Nanosize, sub-nano (clusters) and atomic-dispersed ZnO were prepared for the high-temperature desulfurization. An enhanced absorbance of the nanosize ZnO at 9668 eV is found by X-ray absorption near edge structure (XANES) spectroscopy. ZnO clusters are also observed in the channels of MCM-41. By temperature programmed sulfurization (TPS) and oxidization (TPO), it is found that the nanosize ZnO can be effectively sulfurized and regenerated (with air) at 940-950 K. The smaller ZnO clusters in MCM-41 can be sulfurized at relatively lower temperatures (700-820 K). The atomic dispersed ZnO on TiO2 having the strong metal-support interactions cannot be sulfurized at the temperatures of <960 K, and interestingly a small amount of ZnS can be regenerated at much lower temperatures (i.e., <650 K). It seems that the nano- or sub-nano-(cluster)-size dispersed ZnO may be desired for the high-temperature desulfurization especially for a high efficiency IGCC based electric power generation process.