Effects of accompanying ions on Cu²⁺ and Pb²⁺ adsorption on soil colloids in Shaanxi were investigated by surface complex model. Results indicated that pH(pH₅₀), when Cu²⁺, Pb²⁺ adsorption percentage by tested soil colloids approached to 50%, showed a trend of Cl^- > SO₄^2- > oxalic acid> citric acid > NO₃^- in every ion system;that in terms of Cu²⁺, Pb²⁺+ complex constants (logK_M^int) the order was just the other way round;and that specific adsorption characteristic values (n), reflect ing proportions of specific adsorption and electrostatic adsorption, showed a trend of NO₃^- > Cl^- > SO₄^2- > oxalic acid> citric acid.