A novel, rapid, and high efficiency method to purify natural punicalagin by preparative HPLC is described. The optimum purification condition for punicalagin purification was 14% methanol in 0.1% trifluoroacetic acid solution as the mobile phase. The flow rate was 12ml/min. 81.7mg punicalagin at 98.05% purity was obtained from 300mg crude extract containing 30% punicalagin. The stability of purified punicalagin was also studied. Heating, solar radiation, the pH value, and a strong oxidizer decreased its stability in water. Fe3+ and Cu2+ were complexed by punicalagin. Punicalagin was stable with ultrasonication, ultraviolet radiation, and commonly used food and cosmetic additives.