Fe2+ has an important effect on the production of hydrogen in a biological way. With the brown sugar as the substrate, the effect of biotechnology hydrogen production capacity of the Fe2+ concentration ranging from 0-1650 mg x L(-1) on the condition of anaerobic fermentation was studied. The results showed that appropriate divalent ions had the ability to enhance the hydrogen production. Biogas amounts and hydrogen content increased with increasing Fe2+ concentration from 0-450 mg x L(-1). Compared with the control group increased by 40.75%, the maximum biogas amount of 17.72 L was obtained at Fe2+ concentration of 450 mg x L(-1). And at the same time, the hydrogen content was 60.01 percent. Biogas amounts and hydrogen content decreased gradually when the concentration of Fe2+ was higher than 450 mg x L(-1). Therefore Fe2+ is one of important engineering parameters for the fermentative hydrogen production.