Abstract: Low temperature plasma as a technology for surface modification of materials has a good application prospect in catalyst modification field. The CuO / Al2 O3 catalyst was treated by O2 plasma in a dielectric barrier discharge (DBD) reactor. The effect of plasma treatment sequence on the performance of CuO / Al2 O3 catalyst in the combustion of methane in ventilation air was investigated using catalytic combustion experiment and SEM,BET,XRD,and XPS characterizations. The results show that the modification of catalyst after calcination is preferred because it could im- prove the catalytic activity of CuO / Al2 O3 catalyst for the combustion of methane in ventilation air. The CuO grain size of the catalyst prepared by plasma treatment before calcinations is eight times larger than that of the catalyst obtained after the calcinations. As a result,the CuO dispersion of the catalyst surface is significantly reduced,which affects the catalytic effect. The reason for the larger agglomeration of the CuO particles prepared by the first plasma treatment is that the plasma treatment weakens the force between the Cu and the support Al2 O3 and increases the size of the CuO particles during the subsequent calcination. At the same time,the specific surface area and pore volume increase with the post-plasma treatment compared with the first plas-ma-treated catalyst,while the pore size decreases. The sequence of plasma treatment do not change the chemical valence of copper in the catalyst.