Research on anaerobic fermentation biohydrogen production from molasses wastewater in a continuous stirred-tank reactor (CSTR) was conducted. Emphasis was focused on the rapid start-up of ethanol-type fermentation in biological hydrogen production reactor. It was found that an initial biomass of 17.71 g/L, temperature of 35°C±1°C, hydraulic retention time (HRT) of 6 h, the reactor could start-up the ethanol-type fermentation at the range of 2000-4000 mg/L and at pH from 3.23 to 4.39 in 12 days with COD (chemical oxygen demand), respectively. The content of hydrogen was 45.77% in the fermentation biogas and the COD removal was 8%. As the hydrogen production system experienced low pH (3.23-4.0), the ethanol-produce bacterial can resume easier compared with other fermentation bacteria which are difficult to restore. In addition, when the pH value ranged from 4.0 to 4.63, the hydrogen production increased with the content of ethanol in liquid fermentation products increased. However, it was detected that the yield of hydrogen decreased with a high content of ethanol in the pH value ranged from 3.23 to 4.0, which demonstrated pH value played the most important role on hydrogen production within low pH.