The physical properties lower limits of oil-gas charging in tight sandstone reservoirs are identified through a large number of core test and analysis data. The Chang8 reservoir types, pore-throat structure, and physical properties were clarified. Methods such as oil-gas occurrence, displacement pressure, physical property statistics, oil recovery index, and minimum pore-throat radius were employed to determine the current reservoir physical properties lower limit. By integrating the period of hydrocarbon accumulation and pore evolution, the critical physical properties during oil-gas charging were inverted. The results show that the reservoir types of Chang 8 are mainly feldspar sandstone and lithic feldspar sandstone in Fuxian area, with complex pore-throat relationship. These reservoirs are classified as tight reservoirs with low to extra-low porosity and extra-low to ultra-low permeability. It is preferred that the physical properties lower limits of the current reservoir are 7.0% and 0.15 mD, respectively. For inversion of oil-gas charging in Phase Ⅰ（192.5 ~ 152.0 Ma), the lower limits of physical properties are 20.8% and 7.37 mD, respectively, for oil-gas charging in Phase Ⅱ（152.0 ~ 126.0 Ma), the lower limits of physical properties are 8.2% and 0.22 mD. For oil-gas charging in Phase Ⅲ (65.0 ~ 36.5 Ma), the lower limits of physical properties are basically consistent with the current lower limits of physical properties. The research findings provide an significant geological basis for the evaluation of reservoir and the prediction of favorable in the study area.