Black phosphorus (BP) has become a novel focus of the 2D material due to its natural direct band gap and high carrier mobility, but researchers seldom refer to the water-BP interfacial properties while the natural rippled surface of the BP raises great hope to develop the controllable fluid transmission devices. In this paper, the interfacial slip and friction between monolayered BP and water are first investigated using classical molecular dynamics simulations based on the BP sheet-water Couette model. The results show that the rippled structure of the BP surface leads to the anisotropic boundary slip and interfacial friction between water and BP sheets. The maximum boundary slip and the minimum interfacial friction are obtained for the water flow direction parallel to the ripple direction of BP monolayer. With increasing the intersection angle between water flow direction and BP ripple direction, the boundary slip decreases and the interfacial friction increases continuously. The mechanism of the anisotropic interfacial properties is clarified from the configuration of the water molecules adjacent to the BP surfaces. This finding will generate excitement in designing the BP-based fluid transmission device.