Abstract: Simultaneous photoreduction of Cr(Ⅵ) and photooxidation of methyl orange in water induced by Fe(Ⅲ)-OH complex was investigated under radiation of 250 W metal halide light (λ≥ 313 nm). Significant enhancement of photoreduction of Cr(Ⅵ) and photooxidation of methyl orange was achieved. The optimum pH value was 3.0 for simultaneous photoreduction of Cr(Ⅵ) and photooxidation of methyl orange in the water containing Fe(Ⅲ), Cr(Ⅵ) and methyl orange with initial concentrations over the range of 25～200 μmol/L. The increase of initial concentration of Fe(Ⅲ) was favorable to both photoreduction of Cr(Ⅵ) and photooxidation of methyl orange. As for the influence of the initial concentration of Cr(Ⅵ) on its photoreduction rate, the optimum value was 25 μmol/L, while photooxidation rate of methyl orange decreased with the increase of initial concentrations of Cr(Ⅵ) and methyl orange.