Using attapulgite as the improved isolation wall material， the effects of attapulgite content， phenol concentration， the action of dry-wet or freeze-thaw cycles on the permeability coefficient of the isolation wall were invesgated through permeability test. Combined with nuclear magnetic resonance test， the internal pore structure was studied， and the influence of attapulgite on the anti-seepage effect of the isolation wall was discussed. The results show that the permeability coefficient decreases with the increase of attapulgite content， and increases with the increase of dry-wet or freeze-thaw cycles， and does not change with the change of phenol concentration. Attapulgite can reduce the permeability coefficient of the isolation wall under the action of dry-wet or freeze-thaw cycles，and the distribution of small pores in the isolation wall decreases and the number of mesopores increases with the increase of dry-wet or freeze-thaw cycles. Attapulgite can enhance the anti-seepage effect of the isolation wall， and also restrain the damage caused by the action of dry-wet or freeze-thaw cycles. The effect of freeze-thaw cycles on permeability coefficient and pore structure of isolation wall is greater than that of dry-wet cycles.