The process of down-the-hole hammer(DTH) drilling is very complex because of its high non-linear,large deformation and damage behavior.For this complex problem,current studies are mainly based on experiments.The process,impacting concrete slab with tungsten carbide button of DTH hammer bit,was simulating calculated by non-linear finite element software LS-DYNA3D on concrete model,the effects of different target mesh sizes of concrete on impaction force,impact velocity and penetration depth was discussed.