Abstract: Browning occurs throughout the whole processing and storage of fruit and vegetable juices, among which non-enzymatic browning caused by phenols being particularly important. In this process, phenols are oxidized and further polymerized to form macromolecular brown compounds, which cause color changes. This article introduces the classification of polyphenols, the non-enzymatic oxidation of polyphenols and the main factors affecting the non-enzymatic browning in order to provide an effective theoretical basis for solving the problem of non-enzymatic browning caused by polyphenol oxidation. This has important practical significance for improving the quality of fruit and vegetable juices and extending the shelf life of products.