Abstract: With the POV and AV as measure indicators, three parameters including Carnosic acid, nature Vitamin E, L-ascorbyl palmitate were optimized using L9 (34) arthogonal test for achieving maximum antioxidative effect for algal oil.And then the oxidative stability of algal oil with or without antioxidants were compared by accelerated oxidation test.A combination of 0.7‰ Carnosic acid, 0.3‰ nature Vitamin E, 0.2‰ L-ascorbyl palmitate showed most effective for antioxidation in L9 (34) arthogonal test, the effective order of antioxidants was L-ascorbyl palmitate>Carnosic acid>nature Vitamin E.Rancimat test could determine the oxidative stability and then forecast shelf life of algal oil effectively.Stability test estabilished that the self-life of algal oil treated with multiple antioxidants could reach 21～22 mos while the contrasted one only 10～11 mos.The oxidative induction time of algal oils with or without multiple antioxidants were 49980 and 9850h respectively which calculated through extrapolated method.