Abstract: Fly ash resulted from municipal solid waste incinerator(MSWI)contains high levels of leachable heavy metals and high TEQ dioxins, and is usually classified as a hazardous waste. Thus further detoxification and stabilization treatment are necessary to MSWI fly ash before disposal. The physical and chemical characteristics of MSWI fly ash have an important influence on treatment. Eight types of MSWI fly ashes were collected from several incinerators in China and France. The composition, melting point, crystal characteristic and pore characteristic of fly ash samples were analyzed in details. The results show that the composition is affected significantly by raw material, type of furnace and the position of sampling et al. The melting point of MSWI fly ash is lower than that of coal-waste, because of different content of SiO2. The main crystalline phase for each fly ash is different. The range of inner aperture of fly ash is mainly in the size 0.3 μm～1.5 μm, and the specific surface area is about 20.5 m2/g.