Several typical sulfides were selected and dissolved in hydrotreated base oil, and the antioxidant activities of sulfides studied by rotary bomb oxidation test (RBOT), isothermal pressurized differential scanning calorimetry (PDSC) and non-isothermal PDSC. Four characteristic indexes of constant heating-rate PDSC were chosen and normalized to a comprehensive index by anew method. The sequence determined by the comprehensive index accords partly to the sequence determined by RBOT and accords well with the results reported. The antioxidant activity of sulfide increases with the number of sulfur atoms. Sulfide with long chain has good antioxidant activity, and the antioxidant activity of cyclic sulfides is poor. The method of normalizing the data is useful to determine the oxidation performances of samples, especially when the antioxidant activities vary greatly. (C) 2006 Published by Elsevier B.V.