Abstract: Collapsible loess research of the expressway engineering is basically to adopt the criterion and experiment rules of buildings to investigate and design,due to the working circumstance and mechanics condition different to buildings foundation widely.Applying criterion and experiment rules of buildings directly to collapsibility evaluation and calculation of loess expressway is blindness and inconsequence.The more important is the lack of pertinence.Through the practicability and rationality research on the present criterion to subgrade loess collapsibility,combined the rainfall infiltration depth distributing law,the paper brings forward loess collapsibility evaluation method and model which suitable for expressway subgrade in loess area.