Abstract: Barley bran fermentation liquid was obtained by high-active dry yeast, and the reducing power, scavenging ability of DPPH free radical and scavenging ability of hydroxyl free radical had been measured, researching the influence of different fermentation time on the antioxidant activity of barley bran fermented liquid in vitro.Studies had found that with the increase of fermentation time, polyphenol content in fermented liquid had an obvious rising trend, and stabilized at about 6d, content reached 420.4μg GAE/mL. Compared with 300μg /mL ascorbic acid and BHT, Barley bran fermented liquid showed good antioxidant properties.