To investigate effect of change of ion-strength on change of pH(ΔpH) during successively desorption, a serious desorption tests were conducted on using electrolyte solutions, including de-ionized water, varied in NaNO₃ concentration from low to high, to desorbed successively copper ions or calcium ions adsorbed by two variable charge soils(Ali-Haplic Acrisol from Jinxian of Jiangxi and Hyper-Rhodic Ferralsol from Kunming of Yunnan). To explore relative mechanism further, kaolinite is also be used, and the similar experience processes have also been conducted without the addition of bivalent adsorbing cations. Results showed that de-ionized water and NaNO₃ electrolyte solutions differed in effect on ΔpH, when samples were successively desorbed in de-ionized water, 0.01 mol L^-1 NaNO₃, 0.1 mol L^-1 NaNO₃, 0.01 mol L^-1 NaNO₃, respectively, no matter if the addition of bivalent adsorbing cations, or the type of cations adsorbed (specific adsorption ions or electrolyte adsorption ions). Although the value of ΔpH is different in different condition of desorption and different samples, the tendency of change of ΔpH is just the same. In general, ΔpH was always positive, when the samples were desorbed in de-ionized water, and was generally negative when desorbed in NaNO₃. ΔpH will decrease with the increasing times of desorption in de-ionized water, and will be maintain not change or slight increase when desorbed in the same concentration of NaNO₃ solution for the second or the third times. There is seemly the similar point of beginning of pH_ad (pH of equilibrium suspension of adsorption) for the variable charge soils and kaolinite, which is relative to the ZPC(Zero Point of Charge) of kaolinite, when desorption occurred in de-ionized water and 0.01 mol L^-1 NaNO₃ for the first time. The tendency of change of value of ΔpH of which supporting electrolyte is 0.1 mol L^-1 NaNO₃, is sharper than that supporting electrolyte is de-ionized water, when pH_ad is above the special point, no matter the desorption was occurred in de-ionized water or in 0.01 mol L^-1 NaNO₃. As pHad is higher than that point that above-mentioned, the absolute value of ΔpH will become larger in most situation. For the first desorption in 0.01 mol L^-1 NaNO₃, ΔpH will get the largest absolute value. Because the pH of desorption liquid is just the same as that of the equilibrium suspension of the previous adsorption or desorption, the change of ΔpH should not be attributed to the difference of pH before and after desorbing, it can only attribute to the process of desorption, during which excluded the effect of other factors on ΔpH, for example, the hydrolysis of copper, the similar changes of ion-strength is always existed. According to the theory of four layer and newest report that was about the effect of change of ion-strength on the surface potential of variable charge surface, the increasing ion-strength is always lead to decrease of absolute value of surface potential, vice versa. Base on the above-mentioned observation, it suggest that one of the root causes that lead to this phenomena should be contributed to the change of surface potential of variable charge soils and kaolinite which caused by the change of ion-strength, on the other hand, considering the similar law of change of ΔpH with the increasing pHad, and kaolinite is the main component of the two variable charge soils tested, it can be assumed that kaolinite is the main factors that decide the regular pattern of change of ΔpH caused by the change of ion-strength in variable charge soils.