With the methods of real warhead explosion experiment and numeric simulation etc, the mechanism of trough damage in the airplane by discrete rod is discussed. The effect of the rod's size, velocity on airplane structure damage is discussed. The correlative computing formula is established to forecast airplane structure battle damage. The reason that causes the error between numeric simulation and real experiment is analyzed. The research result is useful to airplane battle damage forecast, evaluation, establishing ABDR prefab plan and survivability design. The results show that as long as the rod has enough speed and the yaw is bigger than 0??, the long penetration damage (trough damage) will be formed on the flat. Because of the damage expanding in the rod penetrating process, the damage width is bigger than the diameter of the rod. When the flat isn't put on the ground vertically, the rod's velocity is vertical to the ground and the yaw is 90?, the trough damage size is longer than the length of the rod. In this condition, an appropriate decrease of flat's yaw can cause the increase of the trough damage.