Abstract: The flow of groundwater in fractured rock mass mainly depends on the hydraulic conduction characteristics of fracture network, especially for low permeability rocks, such as granite. It is necessary to clarify the variation of fracture permeability with stress for long-term safety assessment of underground projects, such as deep geological repository for high-level radioactive waste disposal. This study focuses on the influence of material hardness and fracture contact characteristics of granite on permeability of a single fracture. Water flow-through test on a single fracture was conducted on three materials with different hardness, i.e., aluminum alloy, engineering plastic (PEEK) and granite, and permeability of a single fracture was measured under the confining pressure varying from 3 to 20 MPa in a loading-unloading cycle. Experimental results show that permeability of a single fracture decreases nonlinearly with the increase of confining pressure, and will not completely recover when the confining pressure was unloaded to the initial value, which means that permeability hysteresis occurred. We define the ratio of permeability change of the single fracture subjected to loading-unloading as hysteresis coefficient. Experimental results show that hysteresis coefficient of the smooth fracture in granite and aluminum alloy are 76% and 99%, respectively, while it is about 60% in PEEK. Lower hardness leads to higher permeability hysteresis. Next, we employ finite element method to simulate evolution of contact and permeability of different granite fractures subjected to loading-unloading of confining pressure. Permeability hysteresis behavior of granite single fractures is consistent with the experimental observations. Simulation results show that contact area on the fracture surface distributed unevenly, and higher initial contact ratio causes more plastic deformation at the fracture surface during the loading-unloading process, Permeability hysteresis coefficient has an approximately linear relationship with the logarithm of the contact ratio of the single fracture.