The shale gas reservoirs are featured as low porosity and ultra-low permeability. Nowadays，the key approach to enhance oil production in shale gas reservoirs and other unconventional reservoirs is multistage hydraulic fracturing in hori? zontal wells. However，the mature analysis method of pressure decline fit for fractured vertical wells cannot be applied to the pressure decline analysis after multistage fracturing directly，owing to the differences in flowing characteristic of fractur? ing fluid between several cracks closure in the horizontal wells and single crack closure. Considering stress sensitivity caused by natural crack closure and geological features of natural micro-fractures development in the shale gas formations， dual-pore media model was adopted to simulate the process of fracturing fluid filtration. Meanwhile，pseudo-three dimen? sional fracture model based on elastic-plastic theory was applied to obtain volume conservation equation of the cracks. Con? sequently，pressure decline model during shut-in period under the condition of natural closure of the fractures in the shale gas reservoir was established. The porosity of matrix，the permeability of fracture and the stress sensitivity coefficient are the main factors influencing pressure decline in the shut-in period.