In order to improve the utilization rate of soybean umbilicus in soybean processing industry and to give full play to the nutritional value of soybean umbilicus, a high performance liquid chromatography (HPLC) method for the determination of isoflavones in soybean umbilicus was established based on the national standard method for the determination of isoflavones in soybean. In this experiment, the optimal extraction process of soybean isoflavone was achieved by single factor experiments and orthogonal experiments, when soybean umbilicus and ethanol-water solution served as the raw material and extraction solvent, respectively. The results showed that the order of factors on the extraction rate of soybean isoflavones was: Extraction temperature (B)>Extraction time (C)>Solid-liquid ratio (D)>Ethanol concentration (A). And the optimum conditions were as follows: the ethanol concentration was 80%, the extraction temperature was 80 ℃, the extraction time was 1.5 h, and the ratio of material to liquid was 1:35 (g/mL). Under this condition, when the soybean isoflavones were extracted for three times, the highest extraction rate of 10.88±0.120 mg/g could be obtained. This method is accurate and efficient, and more than 90% of soybean isoflavones can be extracted from raw materials. The extraction process is stable and feasible, which can provide theoretical basis for the extraction of isoflavones from soybean umbilicus.