Permeability jail，where both gas and water cannot flow effectively，may exist in the relative permeability curve of cores of tight gas reservoirs whose permeability is below 0.05 mD. The investigation of gas and water flow in the permeability jail of the tight sandstone cores in the Western Sichuan Basin should be based on the reasonable determination of permeability jail boundaries. A method to determine permeability jail boundaries of the tight sandstone cores from the Western Sichuan Basin was proposed. Factors including relative permeability factor at the cross-over point，gas relative permeability curvature factor and water relative permeability curvature factor were defined to describe the properties of rock and fluids.The method was applied to study permeability jail boundaries of tight sandstone cores from the Western Sichuan Basin.And the influence of permeability jail on gas production of the tight sandstone gas reservoir was analyzed. Results show that permeability jail of tight sandstone cores from the Western Sichuan Basin occupies water saturation region ranging from 63% and 91%，which approximates the initial water saturation of the Sichuan Basin（40%-70%）. During the gas development，due to drilling，well completion and hydraulic fracturing fluids retention in the reservoir，water saturation near wellbore areas can rise to permeability jail and then reduce gas production. The permeability jail has the most significant effect on gas production at the beginning of the production in the tight sandstone gas reservoir. It can delay the peak gas production for hundreds of days.