Abstract: The effect of Fe₃O₄ nanoparticle addition on photo-fermentative bio-hydrogen production process is investigated. HAU-M1 is taken as photo-fermentation bacteria,and corn straw is used as substrate. When the concentration of Fe₃O₄ nanoparticles with 60 nm particle size is 100 mg/L,the specific hydrogen yield reaches（46.68±1.00）mL/g VSS,which is increased by（33.11±0.01）% compared with the（35.07±0.56）m L/g VSS of the control group. The energy conversion efficiency was also improved by 33.10%. The results of hydrogen production kinetic analysis also showes that Fe₃O₄ nanoparticles have a significant effect on the reaction system. When the concentration of Fe₃O₄ nanoparticles with a particle size of 60 nm is 100 mg/L,the maximum hydrogen production potential and the maximum hydrogen production rate are 46.97 mL/g VSS and 1.06 m L/（gVSS·h）,respectively. The suitable particle size and concentration of Fe₃O₄ nanoparticles can significantly promote the hydrogen yield capacity through photo-fermentation pathway,while the high concentration of Fe₃O₄ nanoparticles can inhibit it. The experimental results provide a scientific reference for further improving the theoretical system of photo-fermentative bio-hydrogen production from straw biomass.