Abstract: The chemical composition and mineral phase of waste incineration fly ash are the intuitive expression of its internal mineralogical information. In order to clarify the basic physical and chemical properties of waste incineration fly ash,X-ray fluorescence spectrometer,X-ray diffraction,BET specific surface area analyzer,scanning electron microscope,electron probe and other detection methods were used to study the chemical composition,mineral phase structure,pore and specific surface area,and element occurrence morphology of two typical waste incineration fly ash produced in Northwest China. The leaching toxicity of two typical waste incineration fly ash was analyzed by the toxicity characteristic leaching procedure( TCLP). The results show that the main chemical composition of fly ash produced after incineration of sludge garbage and domestic garbage are Ca O,SiO_2 and Al_2O_3,accompanied by heavy metal toxic elements such as Pb,Cr.The mineral phase of sludge incineration fly ash is mainly aluminum phosphate,quartz,calcium aluminosilicate,mixed with iron oxide ore phase,and its toxic metal species are less and dispersed in the fly ash,only a small part of Ti is combined with aluminum Silicates.The mineral phase of the fly ash from domestic waste incineration mainly exists in the form of calcium aluminosilicate phase and is mixed with some soluble chloride salts. S/Ca and Ca/Si/Al are relatively enriched in the fly ash from domestic waste incineration,other elements are combined with Cl,and toxic metals are various and dispersed. Through TCLP leaching experiments,it is found that there is the possibility of heavy metals leached in incineration fly ash. Therefore,it is necessary to properly dispose of waste incineration fly ash to reduce its environmental risks.