In this work, the Fe2O3-SiO2 composite photo-Fenton catalyst was designed and synthesized as a photonic crystal with a hierarchical macro-mesoporous structure, which possesses a slow-light-effect region that overlaps with the absorption spectrum of methyl orange (MO). The prepared material exhibits remarkably high and stable photo-Fenton catalytic performance for the degradation of MO using only a low concentration of H2O2 under visible light irradiation. The catalytic activity of the as-prepared material is better than that of the corresponding macroporous or mesoporous Fe2O3-SiO2 composites as well as commercial Fe2O3 or the homogenous photo Fenton system of FeCl3 center dot 6H(2)O. The efficient use of H2O2 and the high catalytic activity are attributed to (i) the excellent adsorption of MO by the hierarchical macro-mesoporous structure and (ii) enhanced light harvesting from coupling the absorption spectrum of MO with the slow-light-effect region of the photonic crystal. This hierarchical macro-mesoporous Fe2O3-SiO2 photonic crystal is expected to be a promising cost-effective photo Fenton catalyst for degradation of a variety of dyes by deliberately tuning its slow-light-effect region, and opens up new perspectives for the development of highly efficient photo-Fenton catalysts for environmental re mediation technology.