NOVELTY - A hexaaluminate metal oxide catalyst contains cation containing aluminum complex oxide (I).    USE - Hexaaluminate metal oxide catalyst is used for selectively catalyzing, reducing and denitrating processes, fluidized and catalytically cracking of gas during nitric oxide catalytic reduction, and treatment of smoke of boiler for electric stations (all claimed).    ADVANTAGE - The hexaaluminate metal oxide catalyst having excellent wear resistance and thermally stability is stably and economically manufactured, with high yield.    DETAILED DESCRIPTION - A hexaaluminate metal oxide catalyst contains cation containing aluminum complex oxide of formula: AB'xAl12-xO19-d (I).    A = lanthanum, calcium, potassium, strontium, barium, or aluminum ion (Al3+) (all substituted by transition metal element);    B' = metal atom substituted by Al3+;    x = quantity of atoms in hexaaluminate molecule;and    d = counting rate parameter.    An INDEPENDENT CLAIM is included for preparation of hexaaluminate metal oxide catalyst, which involves using lanthanum-manganese-aluminum oxide (LaMnAl11O19) as catalyst and chemical counting ratio of lanthanum nitrate/manganese nitrate/aluminum nitrate is 1:1:11 or using lanthanum-manganese-aluminum oxide (LaMn2Al10O19) as catalyst and chemical counting ratio of lanthanum nitrate/manganese nitrate/aluminum nitrate is 1:2:10, weighing nitrates of transition metal, alkaline metal and rare earth metal to prepare catalyst (5 g), mixing solid nitrates, adding mixture to deionized water (100 ml) to obtain mixed solution, heating mixed solution at 60 degrees C, rapidly adding ammonium carbonate as precipitant and controlling pH of mixture to 7.5-8, aging mixture for 3 hours, centrifuging mixture and drying mixture at 120 degrees C for 12 hours to obtain powdery catalyst precursor, or blending catalyst at 80 degrees C, dripping excessive citric acid solution, or polyethylene glycol and citric acid solution or cellulose solution, aging mixture, centrifuging precipitate and drying mixture to obtain catalyst precursor crystals, or mixing Triton X-100 (RTM: nonionic surfactant), n-hexanol as auxiliary surfactant and cyclohexane as oil phase in volume ratio of 1:1:2, adding portion of mixture to concentrated ammonia water to obtain reverse-phase emulsion (a), preparing nitrate solution with total ion concentration of 0.75 mol/L, slowly dripping obtained nitrate solution to other mixed liquid to obtain microemulsion (b), adding predetermined amount of microemulsion (a) to microemulsion (b), strongly blending mixture for 1 hour, aging for 24 hours, centrifuging and drying for 24 hours to obtain catalyst precursor, milling obtained catalyst precursor, adding catalyst to a muffle and roasting catalyst.