Four variable charge soils from south China and one constant charge soil from Nanjing were used to examine the effects of ionic strength and pH on the surface charge of soils and adsorption of Cu²⁺ ions.Adsorption of Cu²⁺ was measured at different pH in water, 0.01 mol L^-1, 0.1 mol L^-1 and 1 mol L^-1 of NaNO₃ solutions was measured respectively.In the soils studied, the net surface charge decreased with an increase in pH.The pH at which the net surface charge was zero (pH₀) differed between the soils.The pH₀ was higher for soils dominated by variable charge components.For all soils studied, the adsorption of Cu²⁺ increased with an increase in pH and was closely related to the negative surface charge.The effect of ionic strength on Cu²⁺ adsorption differed between the soils.For constant charge soils, the adsorption of Cu²⁺ always decreased with an in crease in ionic strength irrespective of pH.For variable charge soils, the effect of ionic strength on adsorp tion of Cu²⁺ was much smaller than that for constant charge soils.The higher the content of iron oxide in soil, the smaller the effect of ionic strength on Cu²⁺ adsorption.For iron oxide, the amount of Cu²⁺ ad sorbed in 0.01 mol L^-1 NaNO₃ solution was larger than that in water.The results suggest that the Cu²⁺ ions were retained by both non specific and specific bonding.For constant charge soil, non specific bond ing played an important role in the adsorption of Cu²⁺;whereas for variable charge soil, specific bonding played an important role in the adsorption of Cu²⁺ ions.