Abstract: In order to study the permeability of the groundwater reservoir dam, the stress-strain-permeability coefficient of the experimental specimens was studied by using the laboratory similar simulation experiment method using the electro-hydraulic servo rock mechanics tester. The experiment analyzed the variation of the permeability coefficient of different lithological samples under different external stress changes. The study shows the variation of permeability coefficient of different lithologic rocks during deformation and failure: the porosity of lithology itself is one of the factors affecting the permeability coefficient; and the external stress will change the size and quantity of rock cracks and pores: when the outside world When the stress makes the crack of the sample more tight, the permeability coefficient decreases, and conversely, the permeability coefficient increases. Keyword：goaf; dam; permeability coefficient; porosity; strain