Bio-hydrogen production from diluted molasses by anaerobic activated sludge was investigated in a continuous stirred-tank reactor (CSTR) under condition of continuous flow in this study. Research shows that the reactor started up under the condition of influent COD concentration 3000mg/L, HRT8h, pH6.5~7.5 and (35±1) °C. The process performed steadily and a dominant butyric acid and acetic acid type fermentation population was established, acetic acid and butyric acid accounted for about 80% in the liquid fermentation products. The effluent PH value was maintained about 5.0. The biogas yield could reach at 4.87L/d while hydrogen yield reached 41.25mL/d under the condition. When influent COD concentration rose to 5500 mg/L, the biogas yield and hydrogen yield as high as 9.45L/d and 119.98mL/d were obtained.