Abstract: The rare earth element,europium,was employed to modify the cobalt-based catalyst and to improve its catalytic performance.The cobalt-based composite catalyst doped with europium was characterized by means of TG-DSC,SEM,BET and tested by catalytic combustion of methane to study the effects of polyvinyl alcohol addition and ultrasonic treatment on its structure and properties.The results indicated that the composite catalyst treated with polyvinyl alcohol and ultrasonic possessed distinct porous structure and the catalytic activity of it at 500-600 ℃ was raised by 22%-47% compared to the pure cobalt-based catalysite..