Because of the difficult problem of water injection and liquid production in unconventional reservoirs such as low-permeability and ultra-low permeability reservoirs，this paper systematically discussed the oil displacement mechanism of micro-emulsion flooding for improving oil recovery in low-permeability reservoirs，such as injection pressure reduction and injection ability increase，profile control and water plugging，and reservoir protection. Compared with water flooding，the viscosity of injected micro-emulsion into the reservoir is higher than that of water. Thus，it can improve the oil-water mobility ratio，reduce the viscous fingering of displacement fluids，and reduce interfacial tension（IFT）between the micro-emulsion system and oil phase，which reduces capillary resistance，changes wettability of reservoir rock，and expands the macroscopic sweep volume in the reservoir. In addition，when the micro-emulsion flows through the pore and throat channel of the reservoir，it will also improve the oil-washing efficiency of the reservoir through the synergistic effect of oil solubilization，viscoelastic drag，etc. At the same time， various types and properties of microemulsions（supercritical CO₂ micro-emulsion，nano micro-emulsion，in-situ micro-emulsion， and micro-emulsion foam）with good applicability of oil displacement for low permeability reservoirs were also discussed. The application effect of different types of micro-emulsion in actual low permeability fields was also discussed in this paper. It was found that micro-emulsion flooding can generally reduce the injection pressure of water injection wells in low permeability reservoirs by more than 35%，and the oil increase effect of oil wells was also good. The purpose of this review is to provide a certain theoretical reference for the application of micro-emulsion flooding to enhance oil recovery in low permeability and other unconventional reservoirs.