Abstract: CuO/Al₂O₃-MgO catalyst was prepared by ultrasound assisted dispersion and used in the catalytic combustion of lean methane. The CuO/Al₂O₃-MgO catalyst was characterized by SEM, XRD, XPS, and H₂-TPR and the effect of ultrasonic modification on the structure and catalytic performance was investigated. The results showed that the activity of the CuO/Al₂O₃-MgO catalyst prepared by ultrasonic treatment is much higher than that prepared by the conventional impregnation method. The catalytic activity of CuO/Al₂O₃-MgO is related to both the ultrasonic time and power; the optimum ultrasonic time and power are 20 min and 150 W, respectively. Compared with the conventional impregnation, the ultrasonic modification is propitious to get a catalyst with higher surface area and pore volume, smaller particles, and higher dispersion of active Cu species. Moreover, the ultrasonic modification may promote the formation of Cu⁺ on the catalyst surface and improve the low temperature reducibility. All these can depress the activation energy and enhance the activity of the CuO/Al₂O₃-MgO catalyst in methane oxidation.