ABSTRACT A practicably significant method for preparing camellianin A, which was confirmed by high-performance liquid chromatography–electrospray ionization/mass spectrometry, was established by extracting with water from Adinandra nitida leaves and recrystallizing from 20% ethanol. A yield of about 3.85% (dry mass) was obtained with a purity of 98.9%. The antioxidant activity of camellianin A was evaluated by using different antioxidant tests. The results showed that camellianin A could significantly inhibit lipid peroxidation in a linoleic acid emulsion system, and scavenge 1,1-diphenyl-2-picrylhydrazyl (IC50 2.37 mg/mL) and hydroxyl radicals in a dose-dependent manner. A linear correlation between the concentration and the reducing power of camellianin A was also observed (r2 = 0.9972). PRACTICAL APPLICATIONS Adinandra nitida leaves, abundant in camellianin A, have been consumed as health tea (Shiyacha) and herbal medicine in southern China for hundreds of years. Camellianin A with a high purity was prepared from A. nitida leaves by extremely simple and economical methods, and exhibited a potential antioxidant activity. The results obtained in this study suggested that camellianin A may be widely used in the food and the pharmaceutical industry as a potential natural antioxidant and a functional ingredient.