The invention belongs to the technical field of catalysis, relates to a method for preparing a high-stability methanation catalyst carrier and particularly relates to a method for preparing a high-stability magnesia-alumina spinel catalyst carrier by adopting a hydrothermal synthesis method. The carrier can be applied to the preparation of a catalyst by a dipping method and is especially suitable for serving as a carrier of a methanation catalyst. The methanation catalyst carrier is prepared through adding water and a dispersant which are in a certain ratio into a soluble magnesium salt or a magnesium oxide and a soluble aluminum salt or an aluminum oxide, then, putting the mixture into a high-pressure reactor, carrying out hydrothermal treatment for certain time under the conditions of certain pressure and temperature, carrying out cooling and depressurizing, opening the high-pressure reactor, taking out the material from the reactor, subjecting the material to washing, carrying out filtering, drying, roasting, pelleting and tabletting forming, and then, carrying out roasting. The carrier has good hydrothermal stability; and the methanation catalyst prepared by adopting the carrier has the characteristics that the heat-resisting stability is good, the applicable temperature zone is wide, carbon deposition is not easy under the condition of high CO content, and the like.