Abstract: The volatility and the stabilization of heavy metals in fly ash in municipality & agriculture mixed waste incineration(Type A) and municipal solid waste incineration(Type B) were investigated. And the heavy metals stabilization mechanism was studied by using FT-IR and XRD. The results indicate that the volatility of heavy metals is higher in type B than that in type A, and is significantly affected by the content of chloride in waste source. The volatility of heavy metals in fly ash varies in a sequence of Mn, Cr < Zn, Cu < Pb, Cd. More than 50% of Pb and Cd are volatilized when the temperature exceeds 1 000 ℃. The relatively optimal thermal treatment temperature is 800 ℃and the heavy metals stabilization is higher and the evaporation rate is lower. The primary mechanism of heavy metals stabilization is the formation of stable silicate structure system above 800 ℃.