Abstract: Lotus oligomeric proanthocyanidins ( LSOPC) has good antioxidant activity, but its hydrophilicity based on numerous phenolic hydroxyls limits its application in oil system.In order to increase antioxidation of LSOPC in oils, LSOPC was modified by stearoyl chloride. The effects of reactants ratio, catalyst use level and reaction temperature on the reaction as well as optimization of reaction conditions were mainly studied, antioxidant activity in oils and preliminary molecular characterize of modified LSOPC were also investigated.The results showed that the optimal reaction conditions were 1∶ 2∶ 1.5 of the mass ratio of LSOPC, stearoyl chloride and catalyst, reacting at 40 ℃. Under optimal conditions the POV of overheated rapeseed oil was6.04 meq/kg, which was 31.6% lower than that of control group ( added with LSOPC) .IR spectrum analysis of modified LSOPC showed that cross-linking and esterification was formed between LSOPC and stearoyl chloride from characteristic absorption peaks of methylene, long fat chain and ester groups.So the antioxidation of LSOPC in oils was increased significantly because of its improved lipid solubility.