Abstract: The mechanics characteristics of the different varieties of apples during the different growing periods was investigated and measured.The force transform during the hitting process of hail was calculated,combining the dropping velocity of the hail.The theory of the hail damage on apple was established by using the collision-momentum method.The concept of threshold diameter of damage during the process of the hail damage on apple was put forward.The study revealed the sensitivity of the fruit crops,such as apple to the hail damage.The new concept model for the mechanism of the hail damage of apple was concluded.The results provided a theoretical basis for the benefit analysis of the artificial hail protection.

Key words: Apple, Apple, Hail, Disaster damage model, Hail damage of apple, Sensitivity of apple to hail