Abstract: Groundwater flow 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, and analyzes permeability hysteresis under loading-unloading of confining pressure. Water flow-through test on a single fracture is conducted at confining pressures varying from 3 to 20 MPa in a loading-unloading cycle using three materials with different hardness, i.e., aluminum alloy, engineering plastic (PEEK) and granite. 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 is unloaded to the initial value, which means that permeability hysteresis occurs. We define the ratio of permeability change of the fracture subjected to loading-unloading as hysteresis coefficient. Experimental results show that hysteresis coefficient of the smooth fracture in PEEK and aluminum alloy are 60% and 99%, respectively, while the lowest is about 55% in granite. Lower hardness leads to higher permeability hysteresis. Additionally, 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 larger 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.