Abstract: In the construction of Rock Roadway Drilling and blasting method in coal mine, the key of speed is cutting. With the continuous increase of rock roadway excavation quantities, although the blast hole depth gradually increases, the length of the cut hole beyond the ordinary hole has not changed, which is basically kept at 200 mm and below. Aiming at the problem of over depth of cutting hole and blast hole utilization, the over depth coefficient η The coincidence degree of fracture area is introduced φ By using the mathematical modeling method, the rock stress state during blasting with different ultra depth is analyzed, the relationship between ultra depth and rock crushing expansion coefficient is established, the calculation formula and value range of main parameters of cutting cavity are determined, and it is found that there is an optimal ultra depth coefficient of cutting hole η Coincidence degree with fracture area φ， This results in the highest hole utilization. LS-DYNA numerical simulation is used to analyze the propagation law of explosion stress wave and the stress characteristics of rock at the bottom of cut hole during ultra deep blasting, and the variation characteristics of stress wave intensity at different ultra deep depths are compared; 200mm, 300mm, 400mm and 500mm ultra deep blasting schemes are applied to the rock roadway excavation site respectively. The blasting effect indexes such as single cycle footage, blast hole utilization rate, eye mark rate and block rate of each ultra deep blasting scheme and ordinary blasting scheme are compared. The results show that when the super depth is 400mm, the explosive blasting energy is fully used to break the rock, the energy utilization rate is the highest, and the fracture area formed in the blasting process can be fully overlapped, which provides a free surface for subsequent blasting and improves the rock breaking efficiency, which has a certain guiding significance for the parameter optimization of Rock Roadway Drilling and blasting construction.