Abstract:A high performance liquid chromatographic method was developed for the determination of soybean isoflavones in Natto and Natto Capsule, and the method showed good repeatability and sample stability. Soybean isoflavone were extracted from defatted soybean, Natto and Natto capsule by heating circumfluence method. Four kinds of soybean isoflavone including daidzin, genistin, daidzein and genistein were determined. The results showed that the soybean isoflavones in Natto were 1260mg/kg, which were 30% higher than that in soybean, and the soybean isoflavones in Natto capsule were 11% higher than that in soybean.