Abstract: Steam explosion, as a typical physical-chemical pretreatment technology, destroys the cell wall structure by instantaneous release of high-temperature and high-pressure steam, which promotes the release of plant active ingredients. Appropriate steam explosion pretreatment can significantly improve the extraction rate of free polyphenols, effectively promote the release of polyphenols, and improve the antioxidant capacity. In recent years, steam explosion was applied into the pretreatment of plants and their by-products, and it can significantly improve the extraction of natural active ingredients and enhance functional activity. The influence of steam explosion technology on the content and composition of bound polyphenols and free polyphenols in plants, and the influence on their antioxidant capacity in vitro are summarized in this paper. This would provide a guidance for the use of steam explosion in the food processing industry.