Polyphenol oxidase (PPO) was extracted and purified from Goldnugget loquat and its characteristics were studied. Two protein peaks containing PPO activity were recovered, which were denoted as isoenzyme A and isoenzyme B. A 5.7-fold purification of isoenzyme A with a recovery of 15.3% and 61.1-fold purification of isoenzyme B with a recovery of 98.9% were achieved. Assay of activity of the isoenzymes between pH 3.04 and 7.80 using catechol as substrate showed two activity peaks, one at acidic pH and the other at neutral pH. pH optima of isoenzyme A and B were found to be at 4.5 and 6.8, respectively. Isoenzyme A exhibited a higher activity at acidic pHs than isoenzyme B. They both displayed maximal activity at 30C. Thermal resistance of isoenzyme A was found to be higher than that of isoenzyme B. Effect of inhibitors on the isoenzymes varied markedly.