This study aims to make clear the effect of microstructure design on the wettability and flow directionality. Parallel micro-grooves distort the droplet on it along the pattern because additional energy is necessary to spread across the grooves. The effect of groove design on the directionality was examined based on the experiments. The flow property on the grooves is then examined. The liquid is also easily flow along the grooves. Finally, the applications of the directionality are discussed. This kind of directionality can be used for the design of self-cleaning surface.