Abstract: This paper studied physicochemical and leaching characteristics of three hazardous trace elements As, Se and Pb in hetero-aggregation fly ash (HAFA) and coal fly ash (FA)samples which were collected from coal-fired power plant. The results show that the peak of particle size of HAFA is 138.04 and is 60.26 μm of FA; the fine particles agglomerate into large particles after agglomeration; the contents of heavy metals of As, Se and Pb in HAFA are all higher than those of in FA. The content of heavy metals in gypsum produced in the subsequent desulfurization process is decreased. The batch leaching experiments show that leaching concentrations of three metals in HAFA are suppressed by mild and alkaline condition for As, by acidic and alkaline condition for Se, and by alkaline condition for Pb. The column leaching experiments show that the leaching abilities of the trace elements in HAFA are inhibited in both acidic and aqueous solution.