The coupling between hydraulic and mechanical behavior of the fractured rock mass is of great significance for various civil andenvironmental engineering projects. In order to study the hydro-mechanical behavior of single fracture, seepage tests under differentconfining pressures and fracture water pressures were conducted on single shear fractures produced by triaxial loading of diabaserock samples from Danjiangkou Water Reservoir, China. Test results show that fluid pressure acting on fracture surfaces has stronginfluences on the hydraulic behavior of the fracture. Based on the classic Biot poroelasticity theory and by taking the fracture asassembling of a set of voids in rock mass, a generalized Biot coefficient is introduced to describe the interaction effect between porefluid pressure and fracture deformation. Then, a nonlinear constitutive equation for single fracture under both normal stress and fluidpressure is developed. Later, the mechanical deformation of the fracture is related to the fracture hydraulic conductivity through“cubic law”, so that a coupled mechanical-hydraulic model is proposed. All the four parameters involved in this model have theirphysical significances and can be determined through mechanical compression tests and seepage tests. A first validity of the model ismade by predicting the variation of fracture flowrates versus normal stress under different fluid pressures.