In this paper, cerium based  mixed oxide catalysts were tested in catalytic reduction of NO with CO. Nano crystalline CeO2-MnOx mixed oxide catalysts with Mn/ (Mn + Ce) =0 and 0.25 molar ratio were prepared by sol-gel combustion method. To characterize the physicochemical properties of prepared catalysts the following analysis were evaluated X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and also their activities have been checked for reduction of NOx with CO. The CeO2-MnOx catalysts demonstrated better activity than CeO2 in both low and high temperature. The superior activity of CeO2-MnOx with Mn/ (Mn+Ce) =0.25 molar ratio compare to CeO2 was obtained in 400 oC with 77% NO conversion and 74% CO conversion.