Abstract: Isoflavone derivatives from freeze-dried soybeans were extracted by pressurized liquid extraction (PLE) and determined by reverse-phase high performance liquid chromatography (HPLC) .At the same time ,carry through experiment forinfluence factor about several extraction solvents , temperatures, pressures, etc.as well as establish the optimization of the extraction protocol: 0.1 g of sample, 100℃, three (7min) static extraction cycles and ethanol 70% as extracting solvent. the most rate of picking-up is 93% .The stability of the isoflavones during the PLE was also determined. Indication: degradation of malonyl glucoside forms of the isoflavones takes place using temperatures higher than 100 ℃ whereas degradation of glucosides takes place above 150℃

Key words: liquid extraction, isoflavone, stability, soybean