The Cu²⁺ adsorption on Ca-montmorillonite and δ-Al₂O₃ in the presence and absence of three pesticides, glyphosate, picloram and chlordimeform, was studied. Glyphosate markedly reduced the adsorption of Cu²⁺ on Ca-montmorillonite by complexing with Cu²⁺ ions. The higher the mole ratio of glyphosate to Cu²⁺, the more the decrease of the Cu²⁺ adsorbed. Glyphosate increased the Cu²⁺ adsorption on δ-Al₂O₃ through "bridge" bonding with δ-Al₂O₃ and Cu²⁺. The higher the mole ratio of glyphosate to Cu²⁺, the more the increase of Cu²⁺ adsorbed on δ-Al₂O₃. Picloram also decreased slightly the adsorption of Cu²⁺ on Ca-montmorillonite by means of complexing with Cu²⁺. However, it did not influence obviously the adsorption of Cu²⁺ on δ-Al₂O₃. Chlordimeform decreased the Cu²⁺ adsorption on Ca-montmorillonite through competing for the adsorption sites with Cu²⁺ ions while it showed no effect on Cu²⁺ adsorption on δ-Al₂O₃.