The invention discloses a method for preconcentration of aluminum, lithium and gallium in fly ash and relates to the technical field of resource utilization of solid waste fly ash. The pretreatment method includes the process of fly ash suspension liquid preparation, magnetic separation, screening, concentration, reselection and drying. According to the method, on the premise that no chemical reaction is performed on the fly ash, due to the magnetism, particle size and density properties of the fly ash, a combined separation method of magnetic section-screening-reselection is performed, preconcentration of aluminum, lithium and gallium in the fly ash entering an extraction process is achieved, conditions are mild and operation is easy, the content of aluminum, lithium and gallium in fly ash particles is remarkably improved, the method can be used for the process of performing pretreatment on the fly ash when aluminum, lithium and gallium are extracted from the fly ash, and effective preconcentration of aluminum, lithium and gallium elements can be achieved.