An in vitro study was conducted to determine the effect of different doses of Astragalus root extract (ARE, Huangqi) on rumen fermentation of steam-flaked maize grains. Rumen fluid was taken from 3 crossbred steers fed a 55% forage to 45% mixed concentrate ratio diet. As ARE dose was increased, ruminal ammonia-N concentration was decreased in a dose dependent manner, whereas total volatile fatty acid concentration and total gas production were increased linearly (P<0.001). Increasing ARE doses resulted in decreased molar proportion of acetate and increased molar proportion of propionate as well as a decrease in acetate: propionate ratio. In conclusion, ARE could stimulate the mixed ruminal fermentation as well as modify the pattern of rumen fermentation in vitro.