Abstract：In consideration of water-rock interaction，strength weakening and permeability of the mudstone under different typical stress stages are studied by MTS815.02S servo-controlled rock mechanical test system. Main conclusions are verified by in-situ test using electrical camera. It shows that water-weakened action of specimen is not notable before the peak strength，and the peak strength decreases by 14.5% after affected by water；the water-weakened action is the highest in residual strength stage，steady peak strength decreases about 50%；water-weakened action in plastic stage and elastic stage are in the second place because of self-sealing action of fissures by water argillization action，and the water-weakened action is minimum in the strain softening stage. With the increasing of deformation，permeability variation of specimen is not notable and maintains lower value in the elastic and yield stage. Permeability coefficient begins to increase in the later strain-softening stage and reaches to the peak value in the residual strength stage，and then tends to steady in the plastic compaction stage.
