Abstract: Mechanism of decolorization of rosin by PS-10 was studied.Analysis of the product showed that color of rosin became lighter with the increase of PS-10 dosage,reaction temperature and time. Relative content of abietic-type resin acid decreased from 70.6% to 18.8%,and relative content of dehydroabietic acid and hydrogenated resin acids increased from 7.3% to 30.6% and from zero to 12.2%,respectively.It was proved that PS-10 was a catalyst responsible for disproportionation of rosin,and it was also an antioxidant responsible for decolorization of rosin. Phenolic hydroxyls and sulfur atoms exhibited their antioxidative activities synergistically. Phenolic hydroxyls could capture free radicals, while thioether could decompose peroxide.