The impact of synthesis method on catalytic performances of MnO x –SnO 2 was studied for controlling formaldehyde emission during cold start and warm-up periods of methanol-gasoline/diesel fuel vehicles. MnO x –SnO 2 synthesized by a redox co-precipitation method exhibited much higher activity towards complete oxidation of formaldehyde than that by a conventional co-precipitation one. The results of XPS, XRD and H 2 -TPR characterizations revealed that higher oxidation state of manganese, the formation of solid solution between MnO x and SnO 2 , and more facile redox capability were responsible for higher activity.