Highly ordered Au@Al₂O₃3DOM composites with different pore diameters, including0.48, 0.96, 1.27, 1.49 and 1.65μm, were prepared via infilling Al₂O₃ into the gaps of PS colloidal crystal templates with colloidal crystal template techniquce. The morphology characters and catalytic activity of Au@Al₂O₃ 3DOM composites were characterized by SEM, XRD and UV-Vis spectrometer, respectively. It was found that Au@Al₂O₃3DOM composites had excellent catalytic performance. As the pore diameters increased, the catalytic performance increasedSrapidly and then decreased gradually. The catalytic activity was highest, when the pore size of the composite material reached1.27 μm. The results of theoretical analysis indicated that effective active area and channel transmission efficiency varied with the change of the microstructure, and the competition between the effective active area and the channel transmission efficiency resulted in the chang of the catalytic performance.