The invention discloses a multiphase nickel-based catalyst. The active component of the nickel-based catalyst adopts nickel oxide, a main crystalline phase adopts periclase and spinel, and the weight of the periclase phase is 10.0%-90.0%. The invention further discloses three preparation methods and an application of the catalyst. A large quantity of alkaline elements or oxidoreduction auxiliaries are introduced, and meanwhile, highly nested Ni/MgO and Ni/MgAlO solid solutions are formed through appropriate thermal treatment with a coprecipitation method, an immersion method and a mechanical grinding and mixing method, so that the dispersity of an active component Ni is improved, the binding force of the active component Ni and a carrier is guaranteed, the anti-sintering and anti-carbon capacity of the catalyst is improved, the catalyst has excellent catalytic performance, and the catalyst is applicable to synthesis gas production through natural gas reforming or hydrogen production reaction.