The invention discloses a preparation method and a catalytic application of a supported type high-dispersion nickel-based alloy catalyst. The preparation method comprises the following steps: by virtue of an in-situ growth method, supporting Ni, M (M=Co, Zn, Cu, Fe, Cr and the like) metal in the form of hydrotalcite on the surface of a microsphere-form gamma-Al2O3 carrier with grain size of 20-40 meshes and in a duct of the microsphere-form gamma-Al2O3 carrier, namely growing lamellar precursor LDHs containing Ni and M metal ions outside and inside a Al2O3 particle to form supported type high-dispersion distribution, converting the lamellar precursor LDHs into a corresponding composite metal oxide by drying and roasting at high temperature, and reducing the composite metal oxide to obtain the supported type high-dispersion nickel-based alloy catalyst with NiM distributed on the outer surface and in the duct of the carrier particle. The supported type high-dispersion nickel-based alloy catalyst is applied to first selective hydrogenation reaction of cracked gasoline, so that the conversion rate, the selectivity and the stability of the catalyst can be effectively improved; and moreover, the supported type high-dispersion nickel-based alloy catalyst can be used for methane reforming, and catalyzing reaction of preparing low-carbon hydrocarbon and alcohol by virtue of CO and CO2 hydrogenation.