Abstract: Soil is a medium with microstructure made of particular frame. This paper presents a new model,random soil frame model,according to the microcosmic soil frame and brings forward four basic hypotheses of this model.Based on the four basic hypothesis, the microcosmic soil frame network is obtained. With the numerical calculation of the microcosmic frame network, the mechanical properties of soil can be well simulated. Finally, by means of this model, the process and phenomena of the soil liquefaction is explained in the light of soil frame failure.