The effect of antimony oxide addition to MgV2O6 and Mg3W2O8 was studied in the selective oxidation of hydrogen sulfide to sulfur. Significant improvements in sulfur selectivity and yield were observed for the uncalcined mechanical mixtures of magnesium vanadates with alpha -Sb2O4 Calcination of the mechanical mixtures resulted in the much stronger synergy in catalytic activity and sulfur selectivity. For the uncalcined samples, XRD, TPR and XPS studies indicated that antimony reduction behaviors in the mechanical mixtures differed very much from those in alpha -Sb2O4 alone, suggested that their selectivity improvements might be due to the interactions (probably oxygen transfer) between alpha -Sb2O4 and magnesium vanadates. For the calcined samples, XRD results indicated that their better catalytic performances in H,S oxidation were primarily attributed to the formation of VSbO4 compound from antimony oxide and magnesium vanadates.