Aircraft icing causes a great threaten to flight safety. With the development of anti-icing or de-icing systems for aircraft, some attention has been paid on coating strategies for an efficient way to prevent water remaining on the surface. By application of hydrophobic or super-hydrophobic coatings, characterized by low surface adhesion, shedding of liquid from the surface can be enhanced. The motivation behind this work is to identify the way that wettability affects the motion of runback water, and establish an empirical formula of critical departure diameter. The surface property is characterized by the equilibrium contact angle and the hysteresis angle. The relationship between the air speed and the droplet shedding diameter is studied, corresponding to different surfaces. Then dynamic simulation is conducted combining with the dynamic contact angle model, to investigate water beads movement under high-speed airflow and find out the interaction between water and airflow on different surfaces. Through analyzing the advancing speed of the leading edge and the deformation degree of the liquid droplet, the influence of wettability on liquid droplet shedding is studied. The results also showed that the hysteresis angle plays a more important role than the static angle in droplet shedding.