Fermentative hydrogen production was carried out using a continuous flow stirred tank reactor (CSTR) for the investigation of the hydrogen content in the biogas. Molasses was used as the substrate; hydraulic retention time (HRT) was 6 h; the temperature was in the range of 35±1 .It was showed that hydrogen content increased from 38% to 59% when pH decreased from 5 to 4.6 with oxidation-reduction potential (ORP) increased from -420 mV to -380 mV. The hydrogen content dropped from 50% to 30% as influent COD was improved from4000 mg/L to 6000 mg/L. Hydrogen content increased to 35% when influent COD was improved to 7000 mg/L, however decreased to 25% when influent COD was 8000 mg/L. Ethanol in terminal products is accompanied with hydrogen production but with lower hydrogen content. Butyric acid indicates higher hydrogen content than ethanol.