In order to enhance the yield of SOX produced by Aspergillus sojae ATCC20235,the influence of carbon source,nitrogen source,initial pH and other 8 minerals were first investigated for the first time using the single factor experiment.The orthogonal designs L18(37×21) was carried out based on the result of the single factor experiment,and the optimal condition were listed as follow:carbon sources 30g/L,nitrogen sources 6.8g/L,K2HP04·3H2O 15g/L,MnCl2·4H2O 2 mg/L,BaCl2 500μg/L,H3BO3 1 mg/L,and pH 8.5.Using this optimized media,the yield of SOX can achieve 240U/L.that is 10 times of the initial quantity when using the culture medium given by the US patent.