The invention discloses a preparation method of a Ni/CeO2-Al2O3 catalyst. The preparation method comprises following steps: dissolving Ni(NO3)2.6H2O, (NH4)2Ce(NO3)2, and Al(NO3)3.9H2O in deionized water, then adding critic acid, evenly stirring, placing the solution in a water bath with a temperature of 55 to 65 DEG C, carrying out aging for 23 to 25 hours, carrying out expanding and foaming at atemperature of 95 to 105 DEG C, then burning the reaction product at a temperature of 680 to 690 DEG C for 4.5 to 5.5 hours, and cooling. The method is simple and convenient and is easy to operate. The prepared Ni/CeO2-Al2O3 catalyst has the advantages of large specific surface area, small particle size, and uniform distribution, has many acidic sites and carbon with a large specific surface area,and has a large CH4 conversion rate and high CO2/H2 selectivity.