Polymethyl methacrylate (PMMA) microspheres with diameters of 300-800 nm were synthesized by a modified emulsifier-free emulsion polymerization technique with water-oil biphase double initiators. The obtained PMMA microspheres did not aggregate and their size distribution was narrow. Three-dimensionally ordered macroporous (3DOM) LaMn1-xFexO3 (x = 0, 0.05, 0.1, 0.15) with different pore diameters were prepared by the means of colloidal crystal template method using PMMA microspheres with different diameters as templates. The microspheres and 3DOM catalysts were characterized by means of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformation infrared spectroscopy (FT-IR), nitrogen adsorption-desorption and laser particle size analysis. All the catalysts possessed 3DOM structure with hexagonal well-ordered array. Their macroporous diameters were in the range of 140-600 nm. The catalytic performances of the catalysts for diesel soot combustion were investigated by temperature-programmed oxidation (TPO) reaction. The 3DOM LaMn(1-x)FexO(3) catalysts had good catalytic performances for diesel soot combustion, and their catalytic activities increased with the increasing of pore diameters. (c) 2011 Elsevier B.V. All rights reserved.