LaFe0.5Co0.5O3 catalyst was synthesized by sol-gel method. The catalytic performance and mechanism of LaFe0.5Co0.5O3 for Orange Ⅱ degradation in the present of H2O2 were studied under the condition of pH=3 and 254 nm UV irradiation. The results showed that the decolorization rate of Orange Ⅱ reached 99. 5% after 60 min reaction, the "first" kinetic rate constant of Orange Ⅱ decolorization was 0. 078 min-1, and the TOC removal efficiency was 81. 60% after 180 min treatment. The results of cyclic experiments and physical and chemical characterization of catalyst showed that LaFe0.5Co0.5O3 had high catalytic ability and good structural stability. Based on the results of free radical quenching experiment and analysis of concentration change of total iron ion, ferrous ion, H2O2 and ·OH, it was proved that the catalytic mechanism of LaFe0.5Co0.5O3 included photo-excitation, hole oxidation, superoxide radical oxidation, photoelectron reduction of iron ion, ferrous ion release, homogeneous Fenton reaction and iron ion readsorption processes. In this system, Orange Ⅱ was degradated through synergistic action of Fenton reaction and photocatalytic reaction.