Cracks in soils provide significant preferential pathways for contaminant transport and rainfall infiltration, and water exchange between the cracks and soil matrix is crucial to estimate the preferential flow, which is often quantitatively described by a water exchange ratio. Current studies on the water exchange ratio mainly focus on the crack in sand, but the water exchange ratio between the crack and clay is still unclear. A novel experimental setup was designed with advanced water content and suction measuring system to investigate the water exchange of the deformable cracks in clays. Results show that the water exchange ratio is the highest at the initial stage and decreases with decreasing suction in the clay. The hydraulic conductivity of the crack-clay interface is about one order of magnitude larger than that of the saturated soil matrix. With different initial volumetric water content of soils, the water exchange ratio between crack and soil gradually decreases to 7×10^-6 s^-1 in the process of the infiltration experiments