The physical process of LPG（liquefied petroleum gas）flow dispersion in porous media for the releases at vapor and liquid regions of LPG UST（underground storage tank）was analyzed.On the basis of the mixture model principle，a mathematical model was developed to describe the heat and mass transfer of LPG in porous environment.A series of factors including the LPG phase state，gravity，capillary force，viscous force，gas-liquid interaction and interior resistance of porous media were considered in this model.Based on the Forchheimer equation，the non-Darcy flow equation of the multiphase mixture was presented.The relationship of non-Darcy coefficient and Reynolds number was considered，which could describe the transition of LPG flow in unsaturated porous media from multiphase non-Darcy flow to Darcy flow and extend the scope of model application.Based on the insolubility of LPG in water，the formulation of LPG volumetric concentration was deduced.The model could lead to a good understanding of flow development and impact on environment of LPG in unsaturated porous media and would be a good guidance for site selection，regional planning，and forecasting and prevention of LPG UST accidents.