Abstract: Abstract：【Objective】It is well established that anthocyanin and polyphenol oxidase (PPO) is involved in the pericarp browning of lychee fruit. However, the mechanism by which PPO catalyzes the degradation and browning of anthocyanin has not been clearly understood yet. 【Method】To investigate the role of PPO on anthocyanin degradation, in-vitro degradation of anthocyanin were surveyed in the reactions contained purified anthocyanin, purified PPO or its immobilized style, exogenous phenols, anthocyanidin or its degraded products.【Result】Purified PPO did not catalyze the degradation of purified anthocyanin. However, in the presence of catechol, anthocyanin degraded fast by the action of PPO and formed brown byproducts. PPO catalyzed the oxidation of anthocyanidin or its degraded byproduct directly and formed brown byproducts. Immobilized PPO was used to set up an sequential reaction system of PPO-phenol-anthocyanin, and the results indicated that the degradation of anthocyanin was not dependent on PPO, but only dependent on the quinones generated by PPO.【Conclusion】It was suggested that, during the pericarp browning of lychee fruit, PPO first catalyze the oxidation of phenols, anthocyanidin and/or its degraded products, and form quinones, then quinones oxidize anthocyanin to brown by-products, leading to the decoloring, browning and content decrease of anthocyanin.