The pollution character and migration factor of thallium in the soil profile within the deposed slag collected from a sulfuric acid plant in Guangdong were intensively investigated.The research found that thallium pollutants were mainly concentrated in soils surface layer (0~ 16.5cm) and shown characteristics of contents rapidly decreasing along the uprights.Thallium pollutants have high proportion of labile phases and are mainly in the Fe/Mn oxide fractions(TlFe/MnOx).In the soil the migration capability of thallium in the exchangeable (Tlexc),carbonate (Tlcar) and Fe/Mn oxide fractions (TlFe/MnOx) is strong but organic (Tlorg) and residual fractions (Tires) of thallium have very weak migration capability relative.The first important factor that affected thallium pollutants migration capability in the soil is the condition of soil pH,and Fe/Mn oxide,organic matter,granularity,CEC (Cation exchange capacity) are the second factor.