Abstract: In order to reduce the interference vibration of open-pit step blasting and reduce the peak vibration velocity, based on the measured vibration signal of single-hole blasting in a limestone mine in Hubei Province, through Matlab numerical simulation, the influence of delay time on peak vibration velocity of blasting vibration is analyzed. The results show that the peak velocity corresponding to 0 ms is the largest, and the peak velocity in the range of 1-4 ms delay decreases rapidly with the increase of delay time, in the 10-25 ms time-delay range, the peak vibration velocity of the superposed signal is basically kept below the peak vibration velocity of the single-hole signal, and the resulting blasting vibration intensity is relatively small, and in the 26-39 ms time-delay range, the peak velocity of superimposed signal is slightly larger than that of single-hole signal, and the peak velocity of superimposed signal is slightly larger than that of single-hole signal, the peak vibration velocity of superimposed signal tends to the peak vibration velocity of single-hole blasting. Subsequently, four hole delay schemes of 10 ms, 15 ms, 20 ms and 25 ms are selected to carry out field tests. Based on the measured blasting vibration signals, the blasting vibration strength is compared and analyzed. The results show that the peak velocity of blasting is the largest when the delay time is 20 ms, but the delay time corresponding to the minimum peak velocity is not unique, the vibration intensity of millisecond blasting with 10 ms and 25 ms delay between holes is lower, and the effect of vibration reduction is better.