Abstract:  Based on the nature-history formation conditions of the soil,variability of the soil behaviors is classified in terms of features and the meanings of "variability" are completely clarified.Two modeling methods of soil profiles are compared,and a statistical method of soil variability based on the random field theory is recommended.Simultaneously,a statistical case of analyzing actual engineering investigation data is performed to interpret the superiority of the method.It indicates that the meanings of "variability" are not the difference between layers of soil mass,and that it should be the deviation from point to point in the same soil layer,and can be modeled by the random field theory that is more scientifical than the traditional random variable.The statistical method focuses on considering the distillate of soil variability by separating the certain component that can be depicted by the function of trend and the disturbance component that can be characterized by the random fluctuation efficiently.The study case reveals that the present method will grasp the uncertainties of soil parameters more accurately and provide a favorable way to apply reliability-based design approach in geotechnical engineering.