The invention discloses a method for making a brick by household garbage incineration fly ash. The method includes the steps: (1) curing slurry prepared from the fly ash, MgO, cement and water to obtain a solidified body; (2) crushing the solidified body in the step (1) to obtain fly ash aggregate; (3) homogeneously mixing coal ash, NaOH, the water and the fly ash aggregate in the step (2); (4) curing and forming mortar in the step (3) to obtain the brick serving as a building material. Two gels including hydrated calcium silicate and geopolymers with different crystalline natures are matchedto manufacture the building material, multistage solidification and stabilization of heavy metals in the fly ash and building material recycling of the fly ash are realized, the mechanical performanceof the recycled building material is improved, the process is reliable, equipment and principles are simple, and the household garbage incineration fly ash in different regions and different furnaceprofiles can be safely and efficiently used.