Channel surfaces of 3-D cordierite honeycomb were readily etched with basic solution and became rougher with formation of a uniform layer of silicate nanosheet array structures. The reaction between KMnO4 and Co(NO3)(2) was applied for integrating Mn-Co-O nanosheet array on both blank and modified cordierite honeycombs. The etched cordierite channels can induce the Mn-Co-O arrays with larger unit size, higher density and thickness. Compared to the blank cordierite, the Mn-Co-O array on etched cordierite has much better catalytic performance in oxidation of hydrocarbons, which can be due to its varied features such as more abundant porosity, higher surface area, more Mn4+, Co3+ and adsorbed oxygen species. This study provides an efficient way for tuning the nanostructures of Mn-Co composite oxide nano-array based monolith, further boosting their catalytic activities in combustion of hydrocarbons.