Abstract: During the postharvest storage of Nanguo pear,the content of fruit core and flesh phenolic substance first increased by composing and then decreased by decomposing,and the period of fruit browning corresponded with the period of phenolic substance decreasing. During the same period,polyphenolic oxidase activity reached its peak.So the storage browning of Nanguo Pear was due to that the phenolic substance was catalyzed by polyphenolic oxidase while oxygen existed. Experimental analyses showed, that the content of chlorogenic acid changed significantly after browning. producing brown substance by interacting with polyphenolic oxidase,so chlorogenic acid was identified as one of the important enzyme brown- ing substrates of Nanguo Pear

Key words: Nanguo Pear, phenolic substance, chlorogenic acid