The invention belongs to the technical field of preparation of a light-weight high-strength nano material, and relates to a method for preparing the ultrathin two-dimensional nano materials. The method employs a simple liquid-phase nano-material synthetic method, employs the conveniently obtained metal salt and a buffer solution as the raw materials, and a plurality of the ultrathin two-dimensional metal oxide nano materials. The method comprises the following steps: 1) preparing a target pH buffer solution under room temperature, adding a proper amount of metal salt and graphene oxide, violently stirring the materials until the materials are uniformly dispersed, and forming a transparent solution; 2) heating the mixed solution to the temperature of 60-70 DEG C, reacting the material under stirring condition for 2-4 hours, naturally cooling the material and performing centrifugation washing, and performing freeze drying to obtain the powdery product; and 3) placing the powdery product in a muffle furnace, under air atmosphere, and calcining the material for 2 hours at the temperature of 500-650 DEG C to obtain the ultrathin two-dimensional nano material.