Abstract: The isotherms of the interaction between Cu²⁺, Pb²⁺ and the sediments in the Yellow River were studied by the theory and method of interfacial stepwise ion/coordination particle exchange. The isotherms are stepped, formed by two curves combined together with a “plateau” in the middle. The isothermal equation of surface stepwise ion exchange is applied to calculating equilibrium constants K₁ and K₂of two metal ions by the diagrams. The exchanged adsorption between Cu²⁺, Pb²⁺ and the sediments is stepwise in the Yellow River water.