Abstract: The stability of a pass has great effect on the mine production, on which not only the static load but also impact load act. Among them the latter is the main cause of high rate of failure of the pass. To explore the effect of impact load on the pass, the contact elasticity analysis by Hertz is made to solve the stress in the concrete specimens of different sizes under steel ball impact, and the dynamic analysis software LS-DYNA3D is used to simulate numerically the impact process for the same stress. The two results are compared and reveal that the stress in specimens increases slowly with the increasing impact energy of steel ball especially the increasing size of specimens. It implies that the higher the plastic deformation energy, the more obvious the size effect, thus resulting in the fact that the specimen failure is due to the increase in the frequency of impact.