Capillary barrier is a simple soil layer system which is composed of a finer soil layer underlain by a coarser soil layer. Water infiltrated into soil is retained above an interface between the soil layers, and, in the case of tilted interface, water retained flows downward along the interface. Water flow downward along the interface accumulates its volume of flow due to continuous supply of infiltration water from the soil surface, and begins to percolate into the coarse soil layer at some length of the diversion. This diversion length is one of important parameters to select soil particle contrast between fine and coarse soils and to determine structural dimensions of capillary barrier. In the study the diversion length of capillary barrier was investigated by field observation of soil moisture in the slope and by laboratory soil box experiment.