In view of the problems of long time and low purity of ellagic acid in the actual production process, ellagic acid was prepared using tannic acid as the matrix by a new high-throughput interface oxidation method. The effects of metal ions, tannic acid concentration, temperature and time on the yield and purity of ellagic acid. The influence of solvent method, crystallization method, alkali-soluble acid precipitation method and on the purity of ellagic acid was further explored. The samples were characterized by high performance liquid chromatography, infrared spectroscopy, ultraviolet-visible spectroscopy and thermogravimetry Characterize. The results show that the better process conditions for its preparation are: 2.5% tannic acid solution with metal ion Na (NaOH) to adjust the pH of the reaction solution to 8.5, reaction temperature 20 ℃, reaction time 6h, ellagic acid prepared under this condition After alkali-soluble acid precipitation, the yield is 46.72% and the purity is 84.55%; the methanol solvent washing method was used for 1h at 65℃, the purity of ellagic acid reached 98.13%, and the recovery rate was 75.03%, the thermal stability of ellagic acid was improved. The combination of liquid-gas jet oxidation method and solvent washing method greatly shortens the reaction time for preparing ellagic acid and significantly improves its purity. It is expected to increase the output rate of ellagic acid in industrial production and broaden its application in the fields of medicine and cosmetics.