Abstract: The composition and structure of reservoir porous media are varied. It is di cult to obtain its full parameters, and the accurate description and analysis become di cult as well. In addition, the hydraulic conditions and mechanism of seepage process in porous media are complex, and there also has thermo-hydro-mechanical coupling e ect in porous media. So the current analysis methods and models have certain limitations. This paper presents the REV (representative elementary volume) description method of reservoir porous media. Based on the REV, the author established blackbox model, gray-box model and white-box model of porous media, and proposed "black box → gray box → white box" analysis process in porous media. Also based on black-box and gray-box models, the calculation formulas of REV thermal conductivity were derived, and heat balance equation of heat and mass transfer process was given. Combined with our reservoir thermal recovery situation, this paper analyzed the variation of the thermal conductivity and the characteristics of heat and mass transfer in steam drive, and obtained some useful results. This paper provided a new idea and method to analyze the heat and mass transfer in porous media.