Abstract：By using the triaxial rock mechanics experimental system，testing study is made to analyse the change rule of permeability during the whole stress-strain process and the pore ratio and permeability of sandstone under different confining pressures，and the qualitative and quantitative relationship is established among stress-strain and pore ratio permeability of sandstone. It is shown that during the whole stress-strain process，the permeability reduces slightly with the increase of stress in the elastic stage，after coming the elastic and plastic stage，along with expanding and breakthrough of the induced fracture，the permeability of the rock increases slowly at first and then sharply reaches the maximum value before or after peak point，and at residual flowage stage the existent fracture is pressed closely，and the permeability begins decreasing. The pore ratio and permeability of the sandstone are closely related to the effective confining pressure. The pore ratio and permeability decrease along with the accretion of confining pressure，and conform to the change rule of logarithm function. The sandstone of different diagenesis has different speed and degree in decreasing of pore ratio and permeability. It is shown that under confining pressure the pore ratio and permeability of the sandstone with weaker diagenesis are evidently higher than those of sandstone with stronger diagenesis at decreasing speed and degree. The results obtained from the testing study can be applied into the project of petroleum and gas exploitation，where the variation of in-situ stresses affect the pore ratio and permeability of strata evidently.
