Reducing potato tuber injury rate is responsible for the optimal design of potato harvester, one of the most important goals. To assess the influence of various factors on potato tubers' impact damage, the impact mechanics model of potato tuber was constructed in terms of the deformation and deformation energy analysis during the collision. Secondly, the orthogonal test was conducted. The impact material, potato varieties, potential energy, impact angle were selected as factors. The comprehensive damage index (DI) was taken as the evaluation index. The results showed that the damage degree of potato tuber was decreased with the increasing of coefficient of restitution of impact material, potato yield strength and collision angle, but increased with increasing potato potential energy. When the impact material is a plank, the potential energy is 1.2 J, the type of potato is Lishu No.6, and the collision angle is 15°, the comprehensive damage index is the lowest, 0.0055. According to the result of the orthogonal test, the mathematical regression model was obtained. At the same time, the verification tests were performed. The verification tests showed that the average error between the predicted data of the comprehensive damage index calculated by the mathematical regression model and the experimental data was 5.22%.