The 1~4 grade electric field fly ash is taken as the research object in this paper, the particle size distribution, elemental composition, crystal structure of chemical components, and the presence form of soluble salt components of the original ash samples after water washing treatment are tested, and the crystallization morphology is analyzed to discuss the variation law of chemical composition and specific resistance of different electric field flash ash. The results show that the Fe in the fly ash is mainly in the form of Fe₂O₃, K is mainly in the form of KCl, and a small amount of NaCl is also present; when the number of electric field stages increases from 1 to 4, the percentage of +100 μm particle size in the fly ash decreases from 37.58% to 2.13%, and the specific resistance increases from 3.84 kΩ·cm to 101.1 kΩ·cm; when 4.51% K and 2.05% Na are removed by water washing from the 4-stage electric field fly ash, the specific resistance of dust decreases from 101.1 kΩ·cm to 13.41 kΩ·cm.