To investigate the effect of the O-2 content oil the direct sulfur recovery process (DSRP) combined with the hot gas desulfurization (HGD) process with the unreacted O-2 emitted from the regeneration process, either CO or H-2 was used as a reducing agent for the reduction of SO2 over SnO2-ZrO2 catalyst with a Sn/Zr molar ratio of 2/1. Then, the reaction conditions, including temperature, CO (or H-2)/SO2 molar ratio, and space velocity, were optimized to maximize the sulfur yield in the presence and absence of 1 vol % O-2. The temperature, CO (or H-2)/SO2 molar ratio, and space velocity were varied in the ranges of 300-600 degrees C, 1.0-4.0, and 1000-30000 h(-1), respectively. In SO2 reduction using CO with 1 vol % O-2, the temperature, CO/SO2 molar ratio, and space velocity for the maximum sulfur yield were 600 degrees C, 3.5, and 10000 h(-1), respectively, in which case the SO2 conversion and Sulfur yield were about 85% and 77%, respectively. In SO2 reduction using H-2 with 1 vol % O-2, the temperature, H-2/SO2 molar ratio, and space velocity optimized for the maximum Sulfur yield were 600 degrees C, 3.0, and 10000 h(-1), respectively, in which case the SO2 conversion and sulfur yield were about 89% and 57%, respectively.