Abstract: With no antioxidant soybean oil as medium,the antioxidant activity of sesamolin on soybean oil during heating was researched. Thin-layer chromatography(TLC) and high performance liquid chromatography(HPLC)were combined to detect the transformation of sesamolin during the heating process,the transformation mechanism of sesamolin was also discussed. The results showed that 0.2% content of sesamolin exhibited the good inhibition on inducing soybean oil peroxidation at 180 ℃. The antioxidant effect was good as that of BHT and better than that of vitamin E under same concentration. The antioxidant activity of the combination of sesamolin and phosphoric acid was significant. During the heating process,sesamolin was split to sesamol. Under the influence of phosphoric acid,sesamolin was hydrolyzed to sesamol or the partial was rearranged to sesaminol,which played the antioxidant activity.