Abstract: Groundwater reservoir is one of the effective measures for mine groundwater treatment，but mine water has a weakening effect on the mechanical performance of reservoir dam，which threatens the safety and stability of groundwater reservoirTherefore，it is necessary to carry out the study on the deterioration of rock mechanical properties under the action of mine waterBased on the groundwater reservoir of Lingxin Coal Mine，the deterioration of mechanical properties of gritstone under the effect of mine water immersion was study through laboratoryThe test results show that the mass change of the immersed test piece is related to the specific surface area，the interstitial and the rock mineral compositionUnder small water pressure，the permeability of gritstone is exponentially attenuatedAs the water pressure increases further，the permeability begins to increase as the particles blocking the pores are washed，and the greater the water pressure，the higher the rate of increase of permeabilityWith the increase of immersion time，the tensile strength of rock has a rapid decrease，then slows down and linearly deteriorates；the uniaxial compressive strength first decreases rapidly，then increases slightly，then decreasesThe deterioration of the mechanical properties of gritstone is caused by the infiltration of mine water into the pores of the rock，the ensuing hydration expansion and the dissolution of some minerals in the rockThe increase in uniaxial compressive strength is related to the pore water pressure caused by pore blockage.