Free radicals have close relationship with various human diseases. In the course of free radicals scavenging, antioxidants play an important role. So it is critical to understand the role and capacity of the antioxidants. ORAC (oxygen radical absorbance capacity) assay is the generally accepted standard method for antioxidant capacity assessment. It has the advantages of being similar to physiological condition, simple, good acceptability, high sensitivity, good accuracy and repeatability, high throughput and not easily interfered by human factors. The assay of ORAC has been widely applied in the field of food, health food, phamarcy and medical science. This paper mainly reviewed the development and application of the ORAC analysis. \=