随着数码电子雷管的广泛使用，实现逐孔毫秒精确延时爆破成为可能。为选取最优的孔间和排间毫秒延期时间，基于JKSimBlast爆破模拟软件，在给定的孔网参数和装药结构下，结合矿山常用经验公式，使用二分法设计孔间和排间毫秒延期时间的两因素三水平模拟方案，以最大起爆孔数、质点峰值振动速度和空气冲击压力等参数为指标，选择最优毫秒延期时间。然后，将模拟得到的优选方案与经验方案进行现场爆破试验对比，以爆破块度和爆破振动为指标对爆破效果进行评价。与原方案相比，优化后方案的爆堆大块率从14.30%降至7.94%，测量点爆破振动速度均值从11.682 cm/s降至6.418 cm/s，表明JKSimBlast爆破模拟软件能够较好地进行露天台阶爆破延期时间的优化设计。

Millisecond delay blasting refers to the delay blasting with the interval of several millisecond to tens of millisecond between the adjacent blasting holes. The reasonable millisecond time can make the ore rock fully collide and break，and reduce the production of large blocks. It can weaken or even cancel the stress waves between the blastholes and reduce the blasting vibration. With the wide use of digital electronic detonators，it is possible to realize precise millisecond delay blasting hole by hole. Selecting the optimal millisecond time between holes and rows is of great significance to further improve the blasting efficiency and quality. Based on JKSimBlast blasting simulation software，relying on an open-pit iron mine，under the given hole network parameters and charging structure，combined with the commonly used empirical formula of mine，we design a comprehensive simulation scheme of two factors and three levels，in which the millisecond time between holes is 21 ms，39 ms，56 ms respectively，and the millisecond time between rows is 60 ms，78 ms，96 ms respectively. Taking the maximum number of blasting holes in the same section，the peak vibration velocity of particles and the air impact pressure as indexes，the blasting effect is evaluated. The results show that when the millisecond time between holes is 39 ms and the millisecond time between rows is 78 ms，the maximum number of blasting holes and the maximum number of segments in the same blasting section are both 2，which is the minimum of all simulation results，indicating that the harmful effect of blasting is the smallest. Then，under the condition that the spacing pattern parameter，loaded constitution and layout of priming network remain unchanged，the optimized design scheme of millisecond time is used to design 39 ms between holes and 78 ms between rows，compared with 25 ms between holes and 42 ms between rows，and the delay time in holes is set to 450 ms，The blasting effect is evaluated according to two indexes of blasting fragmentation and blasting vibration. The results show that compared with the empirical scheme，the boulder rate of millisecond time blasting obtained by JKSimBlast blasting simulation software is reduced from 14.30% to 7.94%，with a decrease of 44.5%.At about 200 m away from the blasting center，the average blasting vibration velocity decreased from 11.682 cm/s to 6.418 cm/s，a decrease of 45%. It is proved that JKSimBlast blasting simulation software has the advantages of high accuracy，strong operability，low cost and wide coverage，which provides a new idea for the determination of Millisecond delay blasting time parameters in open pit mining process.