Abstract: In order to explore the dynamic behavior mechanism and essential feature for water droplets in the process of impact in aircraft icing, and improve the precision of numerical simulation of icing, an experimental investigation of the water droplet deformation and its effect on the drag coefficient in the acceleration was conducted by high-speed camera. Four typical forms of the droplet deformation were defined. The relationship between the deformation water and the dimensionless was also analyzed. The coefficient curve and calculation formula of the deformation droplet were also fitted. The results show that the droplet will distort under aerodynamic force, and the shape of the droplet changes from sphere, ellipsoid and saucer to disc. The aspect ratio of the water droplet linearly decreases with the increase of Weber number(We), and hyperbola decreases along with the increase of Bond number(Bo). The deformation of the water droplet will cause the increase of the drag coefficient, and the increase of the drag coefficient is consistent with the deformation process of the droplet.