In the present work, release of hydrogen ions during adsorption of copper ions by variable charge soils was studied.The results showed that there was an abrupt charge in pH on neutralization curve of H, Al-saturated variable charge soils, but no such an abrupt charge in pH could be observed when copperions were added into the suspension of variable charge soils.The two neutralization curves of variable charge soils with and without the addition of copper ions coincided each other when the pH of soil suspension was lower than a certain value, and separated obviously when the pH was higher than that value.It is suggested that no hydrogen ions were released after the addition of copper ions when the pH of soil suspension was lower than a certain value.This pH value was related to the content of iron oxide.The larger the iron oxide content, the higher the pH value.For the majority of variable charge soils, this pH value was about 4.Kinetic studies on the release of hydrogenions during adsorption of copperions by variable charge soils showed that the release of hydrogenions consisted of a rapid process and a slow process.For variable charge soils, the rapid process was getting less and less distinct when the pH approached about 4 from higher value.At about pH4, the amount of hydrogen ions released after 10 min of addition of copperions accounted for only 30% of that after 65 min of addition of copperions.The release of hydrogen ions by adsorption of constant charge soils was much quicker than that by adsorption of variable charge soils.Even at pH 3.8, the amount of hydrogen ions released after 0.5min of addition of copperions accounted for 56% of that after 65 min of addition of copperions.The exchange ratio H/Cu during the adsorption of copperions was larger for variable charge soils than that for constant charge soils.When 0.1 mol L^-1 NaNO₃ was used as indifferent electrolyte in suspension of constant charge soils, the ratio H/Cu increased.