Abstract: In the underground excavation blasting，the setting of the delay time of the electronic detonator is the key factor affecting the blasting effect. Through the theoretical analysis of the delay time setting of large diameter empty hole straight hole cutting blasting，it is proposed to optimize the millisecond delay time correction formula. It is concluded that the cut hole is detonated hole by hole with a millisecond interval of 150~300 ms，and the caving eye and the surrounding eye are detonated at the same delay interval of 50~100 ms. The practice in the excavation of underground roadway in Yinshan Mine shows that the operation safety of the scheme is greatly improved，and the effect is good after blasting.The residual hole of the cutting hole is basically below 20 cm，and the average utilization rate of the excavation hole is more than 93 %，and the phenomenon of residual drug and residual hole is rare.The cross-section of the roadway is regular，the rock block after blasting is uniform，the blasting pile is concentrated，and the economic benefits and social benefits are remarkable.

Key words: electronic detonator, roadway excavation, delay time, blasting parameters