Aggregation/Dispersion behavior of soil colloids is closely related to numerous environmental factors and regulated by surface charges of the colloids. Dynamics of the aggregation of variable charge colloids in yellow earths different in pH was studied with the dynamic light scattering technique. Results show that stability of the aggregation of soil colloids was strongly dependent upon pH. The aggregation of colloids induced by HNO₃ or KOH, different in concentration would exhibit the characteristics of fast diffusion limited cluster aggregation (DLCA) or slow reaction limited cluster aggregation (RLCA). In the former, the aggregation induced by HNO₃ was faster in average velocity and in variation than that by KOH, which suggests that the aggregation induced by neutralization of surface charge was faster than that by compression of double electron layers. The use of the pH corresponding to the turning point where average aggregation velocity changes pH in DLCA to estimate zero point of charge (ZPC) provides a new method for measuring ZPC in experiment.