AbstractAilanthus altissima (Miller) Swingle is a tree used in Chinese traditional medicine as a bitter aromatic drug and in the treatment of colds and gastric diseases. Previous phytochemical studies have demonstrated the presence of quassinoids in the plant, as well as indole alkaloids. The purpose of this work was to determine the phenolic, flavonoid, and total alkaloid contents of the ethanolic, methanolic, acetone, and hydroalcoholic crude extracts of A. altissima and then try to correlate them with antioxidant activity of corresponding extracts. Moreover, the phenolic compounds present in the extracts were analyzed by RP-HPLC. Extracts from leaves have greater phenolic content than the other parts of this tree. Concerning the extraction process, it is possible to conclude that the mixture of water and ethanol is the best solvent to extract substances with antioxidant activity. Analysis by RP-HPLC showed that ferulic acid was the most dominant hydroxycinnamic acid, with an occurrence percentage of 25.59%. These results presented a positive linear correlation between antioxidant activity index and total phenolic content of all the extracts.