Blasting in deep mines is inevitably affected by initial ground stress.In order to explore the rock breaking law of combined holes under high ground stress, the combined rock breaking mechanism of initial stress and combined hole explosion stress was analyzed, and the numerical simulation research on rock fragmentation by combined hole blasting under different stresses was carried out.The results show that the suppression or promotion of the initial stress on the blasting effect depends on the comparison between the initial stress and elastic limit of the rock.When the initial stress is less than the elastic limit of the rock, the effect is inhibited, and when the initial stress is greater than the elastic limit of the rock, the promoting effect is shown.When loading different initial stresses(the rock peak stress is 90.58 MPa), the number of failure units and the crack propagation length of the combined hole are accord with the trend of “decreasing first and then increasing”, and the stress value at the inflection point is 25 MPa, 27.6% peak stress of the rock, which is consistent with the elastic limit stress value in the whole stress-strain curve of the rock.By extracting and analyzing the effective stress and vibration velocity at the measuring point, it can be seen that the coupling stress at the measuring point increases linearly with the increase of the initial stress(20~50 MPa), indicating that the initial stress plays a dominant role under the coupling action of the initial stress and the explosion stress.In the combined hole scheme, the advance cracking blasting creates a new free surface for the front row holes, and the vibration velocity monitoring at the monitoring point shows that the combined hole blasting plan has a good shock absorption effect.