In this paper, a series of mechanical experiments of interface with slurry containing the different capacities of water between the gravel and the concrete are conducted by the monotonic shear apparatus invented by Yangtze River Scientific Research Institute. It is confirmed that the change of water capacity of the slurry will cause that of the curves of shear stress and shear displacement of the interface. When the water capacity of the slurry is small, the relation of shear stress and displacement of the interface is closed to that of the Clough - Duncan hyperbola; in contrast, the relation of shear stress and shear displacement of the interface is closed to that of the characteristics of the rigid plastic shear deformation, which can be analyzed by the rigid - plastic model of Ying Zongze; the water capacity of the slurry has a little affect on the relation of strength and v - stress of the interface, which is still the linear relation. But the big water capacity of the slurry can make the v - displacement bigger and the φ of the interface smaller.