The invention discloses a low-temperature high-efficiency metal composite oxide denitration catalyst and a preparation method thereof. The catalyst is a manganese-titanium composite oxide, wherein a molar content ratio of manganese to titanium is (1-2):(2:1), and the oxide is 40-60 meshes in particle size and 300-400m<2>/g in specific surface area. The preparation method includes: taking a titanyl sulfate aqueous solution as a titanium source and taking a manganous nitrate aqueous solution as a manganese source to prepare a precursor mixed liquid; adding ammonium hydroxide as a coprecipitator into the precursor mixed liquid to realize coprecipitation; subjecting coprecipitates to solid-liquid separation and washing to obtain a primary black brown product, calcining the primary black brown product in an atmosphere furnace to obtain a semi-finished SCR (selective catalytic reduction) catalyst, grinding, and filtering through a 40-60-mesh screen to obtain a finished SCR catalyst. The manganese-titanium composite oxide catalyst is used for flue gas denitration, low in operation temperature, wide in window temperature range and high in NH3-SCR activity in high space velocity and is low in cost, nontoxic and efficient.