The invention relates to a nickel-magnesium-chromium mesoporous composite oxide catalyst for auto-thermal reforming of acetic acid to produce hydrogen. The invention aims to solve the problem that inthe prior art, during the acetic acid auto-thermal reforming process, the structure of a conventional catalyst changes, the active components are oxidized and sintered, and thus the catalyst is deactivated, and provides a novel catalyst having the advantages of stable structure, sintering resistance, carbon deposition resistance, oxidation resistance and high activity. The chemical formula of thecatalyst is (NiO)a(MgO)b(CrO1.5)c; wherein a is 0.08-0.12, b is 0.55-0.92, c is 0-0.33, and nickel oxide accounts for 12.0 to 20.0 wt.% of the catalyst, magnesium oxide accounts for 40.0 to 88.0 wt.%of the catalyst, and chromium oxide accounts for 0 to 40.0 wt.% of the catalyst. A catalyst precursor is prepared by a co-precipitation method, chromium is introduced into the catalyst and is taken asan auxiliary agent; after burning, a stable mesoporous composite oxide catalyst, which comprises a MgCr2O4 and NiCr2O4 spinel structure and a Mg-Ni-Cr-O solid solution, is formed; the reducing performance and stability of the active components are enhanced; at the same time, the hydrogen yield of acetic acid auto-thermal reforming, sintering resistant performance, and carbon deposition resistantperformance are all strengthened.