Abstract: Many large highspeed and long runout landslides could fly in the air at the shortrange stage. The aerodynamic effect was studied for the case of highspeed sliding mass flying at the shortrange stage. The motion differential equations were educed in consideration of the ground effect. Taking the Yigong landslide in China as an example, this paper applied the numerical analysis method to study the flying law of highspeed sliding mass. The calculated results illustrate that, because of the aerodynamic effect to the sliding mass, the horizontal thrust force and vertical lift force both increase. The horizontal speed increases, but its amplitude is little. At the same time, the vertical speed tends to increase more slowly. Therefore, the flying time is longer and the distance is farther than those without consideration of the aerodynamic effect. The results are more reasonable by comparison with the field observation.