Due to higher concern toward health maintenance, the awareness of consuming adequate amount of antioxidant has been increased. Several beverages such as fruit and vegetable juices, green tea and soymilk are known to have antioxidant properties. Meanwhile, ascorbic acid is a compound that may act as secondary antioxidant that is also able to enhance the antioxidant properties of some products. This paper is designed to study the effect of ascorbic acid addition in enhancing antioxidant activity of several beverages which contain different major phytochemical compounds. There are seven beverages that were studied such as carrot juice, tomato juice, broccoli juice, strawberry juice, grape juice, green tea, and soymilk. The parameters analyzed for all samples are the antioxidant activity and vitamin C content. Furthermore, specific analyses were also conducted for each sample such as β-carotene analysis for carrot juice, lycopene for tomato juice, lutein for broccoli juice, anthocyanin for strawberry and grape juices, total phenolic content for green tea, and isoflavones for soymilk. The results show that the addition of ascorbic acid can enhance the antioxidant activity of those beverages with the exception for grape juice. In most beverages analyzed, the increasing of antioxidant activity is followed by the increasing values of each major phytochemicals analyzed. For grape juice, the decreasing antioxidant activity was also followed by decreasing in its anthocyanin level. It is proposed that the reaction between ascorbic acid and anthocyanin could break down the anthocyanin compound.