Abstract: The contents of extractable and non\|extractable polyphenols in different sizes and parts of onion （from the outer to the inner， from the top to the bottom） were studied in this paper. The non\|extractable polyphenols were hydrolyzed by sulfuric acid， and polyphenol contents in the extracts were determined by Folin\|Ciocalteu colorimetric method. The results showed that the extractable and non\|extractable polyphenols were increased with the decreasing size of onion， and the order of extractable and non\|extractable polyphenols was outer>middle>inner， top>bottom>middle in onion. The content of polyphenols was much higher than that of non\|extractable polyphenols in onion

Key words: onion, extractable polyphenols, non\|extractable polyphenols