Abstract: With increasing understanding on the relationship between oxidative stress and the development of various diseases, antioxidants and their antioxidant capacities have received more and more attention in the last two decades. Among the varied methods developed to assess antioxidant capacity, oxygen radical absorbance capacity (ORAC) is one of the widely used methods for in vitro assessment. The principles and advances in analysis methods and applications of ORAC were summarized in this article.