Abstract: In this paper, CeO2 aerogel and Ce1-xMnxO2 aerogel (x=0.05, 0.10, 0.15,0.20) were prepared by sol-gel method and super critical fluid drying technology- Mn/CeO2 was prepared by impregnating CeO2 aerogel with the solution of manganese nitrate. The prepared aerogels were characterized by TEM, BET, CO oxidation reaction and H2-TPR. The experimental results of TEM and BET showed that with the increase of manganese content, the particle size of ceria aerogel decreased and the surface area increased. Reaction of CO oxidation showed that the oxidation activity was improved by adding Mn to the ceria aerogel. The best result was gained when the Mn content is 15 mol%. Ce1-xMnxO2 aerogel (x=0.05, 0.10, 0.15,0.20) and Mn/CeO2 show different carbon monoxide oxidation activities. Catalyst prepared by impregnation method (Mn/CeO2) shows lower catalyst activity than CeO2 and Ce1-xMnxO2(x=0.05, 0.10, 0.15,0.20) areogel. TPR experiment shows Mn species on ceria are also reduced through three steps as MnO2.