Surface charge characteristics of inorganic colloids in soils distributed in different latitudes of China were studied by back-titration method. Results showed that: (1) From south to north, variable surface charge increases with the latitude, which is mainly related to content and composition of soil clay minerals and Fe and Al oxides in the soils. Generally speaking, the higher the content of silicate salt clay in the soil, the higher the permanent negat ive charge and variable negative charge. The higher the contents of Fe and Al oxides, the lower variable negative charge. (2) There exits a peak around pH5 on every Qv-pH curve of inorganic soil colloids from 7 different zonal soils. Maybe it is a result of H⁺ absorption by Si-OH and H⁺ dissociation from Al-OH on the lateral of layer silicates at different pH values. It is possibly related with ZPC of Fe and Al oxides.