Abstract: ZSM-5 zeolites were modified with different contents of monovalent copper by solid-state ion exchange method and used as the catalysts in soot oxidation; the effect of monovalent copper content on the catalytic performance was investigated through extensive characterization. The results indicate that high content of monovalent copper can be loaded on ZSM-5 zeolite by the solid-state ion exchange method, whereas has little detriment to the original micro-structure of ZSM-5. With the increase of copper content in catalyst, the reduction peaks at low temperature and high temperature both shift to lower temperature, while the area of low temperature reduction peak is increased. The catalytic activity of Cu-modified zeolite in soot oxidation decreases after an initial increase with the increase of Cu content. When the Cu loading exceeds 11%, the dispersion of copper species deteriorates, accompanying with a decrease in the catalytic activity for soot oxidation. Meanwhile, the addition of NO to the feed (O₂/He) can enhance the soot oxidation.