The rational selection of space between shot holes is the key to improvement of lump coal rate.The explosion of explosive in the sealed coal body is simulated using finite element software LS-DYNA2D.The research shows that the compressive stress and vibration velocity of particles in coal body reduce rapidly with radial radius and time increasing.The compressive stress and vibration velocity of particles are high near the blasting center,but their duration is shorter;The compressive stress and vibration velocity of particles are away from the blasting lower center,but their duration is more long.At the same time,through the mechanism study of blasting for increasing lump coal rate,the conclusion that adopting small explosive cartridges,controlling space between shot holes and time of delay in millisecond blasting are the main ways to increasing lump coal rate is drawn.It is a kind of feasible research means for optimization of blasting parameters for increasing lump coal rate.