Abstract: In this paper,the influences of antioxidant Na2S2O3,Vc and Cys on mixotrophic fed-batch culture of S.platensis were studied.The result shows that with the antioxidant concentrations increase the cell dry weights gradually increase,but the cell dry weights start to drop to certain concentration of antioxidants after 9 days,according to the standard of the cell dry weight.Each of the highest cell dry weight respectively is 2.42、1.81、1.71 g/L,so the antioxidized effect of Na2S2O3 is the best.