The main affecting factors and adsorption isotherms in the application of natural iron-bearing oxides and hydroxides to the treatment of Hg(Ⅱ) wastewater were studied with the theory of adsorption of heavy metal ions on the surface of water_metal oxides and hydroxides. The results show that such factors as pH, ionic strength, quantity, Hg(Ⅱ) concentration, grain size, temperature,rotation speed and time exert some influence on adsorption rate, with pH playing the strongest role. In addition, the research indicates for the first time that the adsorption of Hg(Ⅱ) on natural iron-bearing oxides and hydroxides shows plateau isotherms instead of Langmuir and Freundlich isotherms, in accord with the isotherm of stepwise ion/coordination particle exchange.