The microbial reduction of ferrihydrite, lepidocrocite, hematite, goethite and Aluminum-subst ituted iron oxides were examined under anaerobic incubation by slurry experiment.The variation of the partial pressure of H₂, CO₂, CH₄ and the acetate concentration were determined.The results indicated that different iron oxides had been shown different reduced ability in slurry.The ferrihydrite and lepidocrocite were easily to be reduced, which had almost same reduced level, meanwhile in the addition of ferrihy-drite, there was a reduced hysteresis.The goethite, hematite, Al-substituted goethite and Al-subst ituted hematite were difficult to be reduced, which showed a same characteristic of iron reduction with control.Iron reduction can cause the decrease of H₂ and acetate concentration, and then methane production was inhibited.By ferrihydrite and lepidocrocite addition, the contribution (%) of electron-transfer belong to iron reduction were respectively increased to 63.32% and 46.90% from 18.30% (control), however, the contribution (%) by methane production were respectively decreased to 35.85% and 52.32% from 80.92% (control).Because of election compet ing consummation of iron reduction, the methanogenesis was greatly inhibited.