The invention discloses a simple semi-automatic method for screening the fly ash with the uniform particle size. The method comprises the following steps of ball milling, pre-sintering, washing, magnetic adsorption, suction filtration, washing, alcohol washing, automatic suction filtration, drying and grinding. According to the invention, the fly ash is recycled through the semi-automation, the fly ash particles with the uniform particle size are separated out, the waste is turned into the wealth, and the development of the environmental protection cause is facilitated. According to the invention, the used instruments are the common and cheap experimental instruments in a laboratory, the semi-automation can be realized, the financial resources, material resources, manpower and resources are saved, and the operation is simple. The fly ash particles with the uniform particle size can be applied to the polymer solid electrolyte, so that the ionic conductivity is improved, and the development of the all-solid-state batteries is promoted.