【Objective】To investigate in depth effects of ionic strength on desorption of Cu(II) pre-adsorbed on surface of variable charges, two variable charge soils, Ali-Haplic Acrisol and Hyper-Rhodic Ferrasol were employed in a successive desorption experiment, in which the soils had been pre-treated with copper ions in de-ionized water or 0.1 mol•L^-1 NaNO₃ for adsorption and were then treated with a series of NaNO₃stripping solutions with concentration ranging from low to high, to desorb the pre-adsorbed Cu(II) from the soils. 【Method】In this study, the two variable charge soils were pretreated with electrodialysis and then subjected to a series of adsorption and desorption tests with varying pH in an attempt to characterize copper ion (Cu(II)) desorption from clay minerals.【Result】Similar to the findings in the studies on kaolinite, Cu(II) adsorption of the soils increased rapidly from 0.05 to nearly 1 in score value within the range of the pH set for this research (pH 3.0~6.3). No matter what concentration of the electrolyte used, all the adsorption score value curves could be fitted with Fischer equation and the degree of fitting reached as high as 0.996 or more. Also it was noteworthy to note that when adsorption occurred in de-ionized water or 0.1 mol•L-1 NaNO₃ solution, the same in pH, Cu(II) adsorption was always higher in de-ionized water than in 0.1 mol•L^-1 NaNO₃ solution in score value, which was attributed to the effect of the high concentration of electrolyte in the solution inhibiting Cu(II) adsorption. The findings of this experiment indicate, 1) that the adsorbed copper ions can be desorbed in de-ionized water and the desorption will decline in score value with desorption going on round after round in the waters the same in pH; 2) that in most cases, pH of the equilibrium liquid remains basically the same, around pH5.0, when the desorption lowers down to almost zero in score value; and 3) that the phenomena of re-adsorption will occur during the first round of desorption in de-ionized water only with pH above a specific pH, when the soils are pre-treated in 0.1 mol•L^-1 NaNO₃ solution, which means the copper ions will be adsorbed rather than desorbed when the equilibrium liquid is above this specific value in pH. Compared to Ali-Haplic Acrisol, Hyper-Rhodic Ferrasol is much lower in Cu(II) re-adsorption threshold. Similar to what happens in kaolinite, the results of sequential Cu(II) desorptions with NaNO₃ solutions varying in concentration from low to high after the soils that had been pre-treated in either de-ionized water or 0.1 mol•L^-1 NaNO₃ solution, were subjected to three rounds of desorption with de-ionized water demonstrate 1) that Cu(II) that could not apparently be desorbed by de-ionized water, can be desorbed by NaNO₃solution, and all the score value curves of pH-desorption follow a trend of rising first and then declining with rising pH regardless of concentration of NaNO₃ or rounds of desorption; 2) that the score value of Cu(II) desorption peaks in 0.1 mol•L^-1 NaNO₃ solution; and 3) regardless of the concentration of NaNO₃, there is a relatively gradual rise process before the desorption begins to soar up in score value. In all the case, Ali-Haper Acrisol is higher than Hyper-Rhodic Ferrasol in Cu(II) desorption score value, and in most cases the desorption score value curve has an apparent turning point where the desorption score value abruptly soars up, regardless of concentration of NaNO₃ and rounds of desorption. Although the desorption equilibrium suspensions are not consistent in pH at the turning points, however, the pH at the turning points corresponding to the pH_ch of the desorption equilibrium suspensions are quite consistent, lingering around a special pH, that is, pH3.5, for Cu(II) adsorbed in de-ionized water, and pH3.18 or pH3.39 for CU(II) adsorbed in 0.1 mol•L^-1 NaNO₃ solution, which means that the copper ions adsorbed near the turning points of the pH-adsorption curves under any adsorption conditions exhibit a similar tendency in the desorption tests, that is climbing gently first and then abruptly soaring up with rising pH of the system. 【Conclusion】All the above-descrobed phenomenon and differences can be attributed to the difference between the two variable charge soils in content of iron oxide and the difference between iron oxide and kaolinite in nature of the surface charge.