Abstract: By using Fe²⁺ and TiO₂ as photocatalysts,the degradations on methyl orange were investigated.The results demonstrated that the reaction was prevented effectively in the fenton reaction system when NaOH was added;the efficiency on photocatalytic oxidation was highest when pH=4 and better when the concentration of methyl orange was lower.The degradation of methyl orange was promoted greatly when photocatalyst was modified and the deposition of FeC₂O₄ disappeared.The photocatalytic activities of H₂O ₂+FeSO₄、H₂O₂+FeC₂O₄、TiO₂ were in turn H₂O₂+FeC₂O₄ >Ti₂>HO₂ >FeSO₄.