Abstract: The theory of meso-micro flow in porous media is a "mysterious key" to unlock the flow of nano-micron porous media. With the advancement of world petroleum engineering technology, unconventional oil and gas reservoirs are main targets for the development of the petroleum industry, which are distributed with a large number of nano-scale pores. For the problem that the macroscopic statistical methods base on Darcy and non-Darcy flow cannot be used to reveal the nonlinear flow mechanism and effective mechanism of multiphase fluids in nano-micron porous media as present. This paper summarizes the research results in this area (including the author). It summarizes the current research status of fine and micro flow in porous media from three aspects: theoretical analysis, experimental research and numerical model. Focus on key issues such as the relationship and characterization of nano-micro-scale fluid flow interface and micro-mechanical properties, meso-macro network simulation, micro-scale fluid (oil/water, gas/water) flow, meso-dynamic mechanism and mathematical