Abstract: Reasonable over-depth can effectively avoid the bedrock and improve the blasting effect. In order to study the influence mechanism of over-depth on blasting effect and the reasonable over-depth value of bench excavation blasting，based on the actual situation of a negative excavation project，the three-dimensional model of open-pit bench was established by ANSYS finite element software，and the stress field distribution law of bench excavation blasting was simulated by LS-DYNA post-processing soft⁃ ware. According to the effective stress time-history curve and damage diagram obtained by numerical simu⁃ lation，the reasonable over-depth of open-pit bench excavation blasting under the combined action of mul⁃ tiple factors was explored，and the optimal blasting parameter scheme suitable for the project was selected. Finally，the blasting engineering effect is the best when the hole network parameter is 2.5 m × 2 m，the ap⁃ erture is 90 mm and there is no over-depth.

Key words: open excavation, numerical simulation, over-depth