Effects of ionic strength of electrolyte solution and narrue of canon on phosphate desorption in some variable-charge clay minerals and soils were studied. It was observed that Ca²⁺-saturated montmorillonite, kaolinite and clay colloid from red soil sorbed more Phosphate than Na⁺-saturated samples, but much less phosphate than Al³⁺-saturated samples. Such differenct was more significant for montmorillonite than kaolinite or soil clay, suggesting that cation bridge mechanism was in action. The bonding strength of formed surface complex depended on the ability of canon to neutralize the negative change on the solid surface and its chemical affinity for phosphate ion. With increasing valence of the canons from Na⁺ through Ca²⁺ to Al³⁺, decreasing phosphate was desorbed at the same adsorption saturation for all tested samples, especially for montmorillonite, due to stronger electrostatic attraction of the cation for both negatively charged surface and phosphate ion.