In order to find out the physical properties lower limits of oil-gas charging in tight sandstone reservoirs. Using a large number of core test and analysis data, the type of Chang8 reservoir, pore-throat structure and physical properties are clarified. Based on the methods of oil-gas occurrence, displacement pressure, physical property statistics, the oil recovery index, the minimum pore-throat radius, etc. to determine the physical properties lower limit of the current reservoir. Combined with period of hydrocarbon accumulation and pore evolution, the critical physical properties of oil-gas charging is 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, which is a tight reservoir 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, respectively, 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 results provide an important geological basis for the evaluation of reservoir and the prediction of favorable in the study area.