Abstract: Preparation of ellagic acid from pomegranate peel by hydrolysis was developed. Pomegranate peel powder was extracted with 60% ethanol by means of ultrasonic -assisted extraction to obtain crude extract. After removal of lipophilic ingredients by extracting with petroleum ether, crude extract was extracted with ethyl acetate, and the ethyl acetate fraction was hydrolyzed to produce ellagic acid. With the ultra performance liquid chromatography-mass spectrometry, the main ingredients in the ethyl acetate fraction were identified as castalagin, punicalagin, granatin A, corilagin, granatin B and ellagic acid, and the hydrolysis product was identified as ellagic acid. The hydrolysis process of the ethyl acetate fraction was monitored by capillary electrophoresis. It had been found that with the increase of hydrolysis time, the number of peaks in electropherogams was reduced, while the weight of ellagic acid increasing. With the orthogonal experiment, the influences of hydrolysis time, hydrolysis temperature, as well as acid concentration on the ellagic acid yield was investigated. It turned out that optimum conditions of hydrolysis were as follows:hydrolysis time of 6h, hydrolysis temperature at 100℃, and sulfuric acid of 1.0mol/L, with the ellagic acid yield of 32.7%.