Abstract: The No.2 open-pit mine in Shuangli mine has complex lithology and high block rate in blasting.As far as possible in order to reduce the specific charge of the situation, determine the double top air in the mine bench blasting interval length, to reduce the large and root, in this paper, nonlinear dynamic analysis by finite element method to simulate the 12 m bench blasting process, according to the stress of the slope equidistant inspection unit interval in central position of value can reach the yield strength of the rock, the yield strength of rock and achieve sustained length of time, get the best air interval length is 4 m, and industrial test is carried out.