Based on the discrete element method, the three dimensional mixed-size grain/bed collision process has been investigated in this paper. By considering the influence of lateral impact angle on the mean ejection velocity and ejection number, we obtain that the mean lateral ejection velocity increases with the lateral impact angle at large mean diameter cases and also increases with the impact velocity, while decreases with impact angle. The simulation results indicate that although the lateral impact affects the mean ejection velocity, its effect on the mean ejection number is very limited. Moreover, the mean lateral ejection velocity is influenced by the impact angular velocity. Based on these studies, a more comprehensive three dimensional mixed-size splash function is given. It is of great significance to the particle motion based on turbulence in aeolian sand landform.