An experiment on the characteristics of Co, Cu, Pb and Zn adsorption by seven highly weathered acid soils derived from different parent materials in different areas of southern China was conducted to study affinity characteristics and factors affecting affinity as well as the mechanism of adsorption reaction by using shapes of adsorption curve, pH values and competitive adsorption equations and distribution coeffieients. Clay fractions(< 11tm) separated from red soils with different properties were allowed to react with solutions of Co, Cu, Pb and Zn in 25 ml 0.05 mol/L Ca(NO₃)₂ as supporting electrolyte containing the desired amount of adsorbate ion, respectively. The pH values of suspention were adjusted by adding appropriate amounts of 0.1 mol/L N0₃ or saturated Ca(OH)₂ solution prior to metal addition to obtain a series of suspentions with various pH values.