This invention relates to a method for preparing heat-insulating and energy-saving lightweight aerated wall bricks, which are prepared from aggregate, gelation agent, aeration agent, heat-insulating material and water. The aggregate is composed of slag or river sand, glass microbeads, floating beads, closed perlite, and expanded perlite. The gelation agent is composed of cement, gypsum and lime. The aeration agent is Al powder. The fiber heat-insulating material is composed of high-Al powder, tripolite, ceramic fibers, mineral wool, sepiolite, expanded vermiculite, glass cotton and palygorskite. The wall bricks have such advantages as high compressive strength, low heat conductivity, high heat-insulating performance, high fireproof and damp-proof performances, rapid and convenient construction, and no need for composite heat-insulating layer.