NOVELTY - Preparing nanocomposite methanation catalyst comprises mixing pseudoboehmite and deionized water to form a suspension, reflux heating, adding nitric acid into the suspension, reflux heating, and cooling to obtain translucent sol gamma -boehmite; adding nano-titanium dioxide powder into translucent sol gamma -boehmite, and stirring; drying, calcining to obtain titanium dioxide/ gamma -alumina nano-powder; taking titanium dioxide/ gamma -alumina nano-powder as methanation catalyst carrier, impregnating in nickel nitrate solution, drying, and calcining to obtain nickel oxide/titanium dioxide/ gamma -alumina catalyst.    USE - The method is useful for preparing nanocomposite methanation catalyst (claimed).    DETAILED DESCRIPTION - Preparing nanocomposite methanation catalyst comprises (i) mixing tetrabutyl titanate and ethanol in the volume ratio of 1:3-1:5, and stirring to obtain tetrabutyltitanate ethanol mixed solution; (ii) mixing deionized water and ethanol in the volume ratio of 1:1, adding nitric acid so as to control the pH to 3-4, to obtain ethanol nitric acid mixed aqueous solution; (iii) at room temperature, slowly dropping ethanol nitric acid mixed aqueous solution into tetrabutyltitanate ethanol mixed solution using peristaltic pump, vigorously stirring to carry out hydrolysis of tetrabutyl titanate, and stirring for 3 hours, to obtain sol; (iv) drying the obtained sol at 80 degrees C for 24 hours, to form a gel, then calcining the gel in a muffle furnace at 500 degrees C for 2-4 hours, to obtain nano-titanium dioxide powder; (v) mixing pseudoboehmite and deionized water in the mass ratio of 1:20-1:40 to form a suspension, reflux heating with stirring at 85 degrees C for 2-4 hours, adding 1-2% nitric acid (1.6 mol/l) into the suspension, reflux heating with stirring for 4-8 hours, and naturally cooling to room temperature, to obtain translucent sol gamma -boehmite; (vi) adding nano-titanium dioxide powder into translucent sol gamma -boehmite, where the nano-titanium dioxide powder accounts for 5-30%, and then stirring; (vii) drying overnight at 105 degrees C, then calcining at 400-600 degrees C for 4-6 hours, to obtain titanium dioxide/ gamma -alumina nano-powder; (viii) taking titanium dioxide/ gamma -alumina nano-powder as methanation catalyst carrier, impregnating in nickel nitrate solution, drying overnight at room temperature, drying at 105 degrees C for 4 hours, then calcining at 400-600 degrees C for 4-6 hours to obtain nickel oxide/titanium dioxide/ gamma -alumina catalyst, or taking titanium dioxide/ gamma -alumina nano-powder as methanation catalyst carrier, impregnating in auxiliary agent metal nitrate solution, drying overnight at room temperature, drying at 105 degrees C for 4 hours, then calcining at 400-600 degrees C for 4-6 hours to obtain metal/titanium dioxide/ gamma -alumina catalyst; where the metal is cerium, calcium, cobalt, lanthanum, zirconium, samarium, barium, manganese, iron, molybdenum and/or copper oxide; and (ix) impregnating the metal/titanium dioxide/ gamma -alumina catalyst in nickel nitrate solution, drying overnight at room temperature, drying at 105 degrees C for 4 hours, then calcining at 400-600 degrees C for 4-6 hours, to obtain nickel oxide-metal/titanium dioxide/ gamma -alumina catalyst. An INDEPENDENT CLAIM is also included for nanocomposite methanation catalyst, prepared as mentioned above.