Abstract: The dispersion mechanism of cohesive soils has not been fully understood because of the complex nature of system. In this study, dispersivities of 123 field engineering soil samples are analyzed and correlated to their major influencing factors (physical properties, mineral properties and chemical properties) using the grey system theory and laboratory certification tests to understand the dispersion mechanism of associated soils. The grey system analysis shows that the chemical properties (e.g. pH of soils) have the highest correlation intensity with the soil dispersivity, with less impacts due to soil sodium and montmorillonite contents. The soils with high dispersivity are routinely observed to have a rich exchangeable sodium content and high pH values. The dispersivity of cohesive soils can not be predicted solely by their sodium or total montmorillonite contents.