The photodegradation of Mordant Yellow 10 (MY10), a kind of azo dye, in aqueous dispersions of H2O2/hematitc (alpha-Fe2O3), goethite (alpha-FeOOH) and akaganeite (beta-FeOOH) at neutral pHs under UV-light irradiation was examined. The fastest degradation rate of MY10 was obtained with goethite. The formation of .OH in the photoreaction process was detected by ESR spin-trapping technique. A possible mechanism of heterogeneous photo-Fenton reaction was proposed.