Since the coal rocks are soft and brittle，and has low mechanical strength，the coalbed methane reservoirs have strong stress sensitivity. In the process of development and drainage，due to the decrease of pore fluid pressure an the increase of effective stress，the pores and fractures in reservoirs tend to close，the porosity and permeability decrease，the compaction degree enhances and the response degree of coal body to stress changes. Based on the theory of mechanical deformation，the varying trend of porosity and permeability of coals under axial stress is calculated through the deduction and establishment of porosity and permeability model coupling mechanical strain. The“average pore compressibility”function is used to replace the pore compressibility constant in the traditional match beam model to form an improved match beam model. Then，the influence of the change of pore compressibility on the pore permeability parameters is analyzed. The results show that the porosity，permeability and pore compressibility decrease with the increase of axial stress；There is a negative exponential relationship between the porosity/permeability and the axial stress；The dynamic variation of pore compressibility with axial stress causes the porosity and permeability to decrease with the decrease of axial stress. Therefore，there is a geological correlation between physical parameters and stress-strain of coalbed methane reservoirs，and the stress sensitivity of physical parameters should be considered when judging reservoir physical properties.