Effect of H⁺ release from four constant charge soils and two variable charge soils on pH of their soil suspensions different in Cu ion concentration and in concentration of electrolyte was studied. Results indicate that for all the six samples, except for yellow brown soil, the higher their Fe content the lower the △pH_max caused by adsorption of copper ions. The adsorption of copper ions showed no significant effect on neutralization curves. When the copper ion was low in concentration, H⁺ release was low, but when the copper ion was high in concentration and the pH value of the system exceeded a certain threshold, a large volume of H⁺ was release. The presence of iron oxide was found to be the main cause for difference in H+ release between constant charge soils and variable charge soils. The effect of electrolyte concentration on the neutralization curves of constant charge soils and variable charge soils after adsorption of Cu ions varied greatly. The higher the iron oxide content, the lower the effect of electrolyte concentration on post-Cu-ion-adsorption H⁺ release.