Abstract: Reactive oxygen species (ROS) have strong relationship with several diseases. Many fermented foods were reported to be important sources for antioxidant compounds. Antioxidant activity of water kefir never reported in the scientific literature. The objective of this study was to detect and investigate the antioxidant potency of water kefir. Water kefir was prepared by fermentation of sugar solution with kefir grains for 24h. Antioxidant activity of fresh water kefir drink and its extract with (0.125–5 mg/ml) was evaluated using 2,2,-diphenyl-1-pricrylhydrozyl (DPPH) scavenging method, and inhibition of ascorbate autoxidation and the reducing power of water kefir were determined, Butylated hydroxyanisole (BHA) and ascorbic acid were used for comparison. Water kefir demonstrated great ability to DPPH scavenging ranged (9.88-63.17%). And inhibit ascorbate oxidation by (6.08-25.57%) increased in consequent with concentration raising. These results prime to conclude that water kefir could be promisor source of natural antioxidants with good potency in health developing.