This paper presents a study of the properties of municipal solid waste incineration (MSWI) fly ash, including their size distribution, pH value, microscopic morphology, mineral components, heavy metal content, and leaching toxicity. It is found that: over 80% of fly ash particles have diameters between 0.105-0.154mm, and the mass ratios of particles smaller than 0.063nun and larger than 0.154min are both lower than 5%; the fly ash particles tend to be strongly alkaline (pH >= 11); their main elements are Cl, Ca, K, Na, Si, Al, 0 and 5, and their main heavy metal elements are Zn, Pb, Cr and Cu....