Blasting technology is more and more widely used in urban foundation pit engineering, but blasting activities may cause certain disturbance to neighboring facilities and environment, and the vibration generated during blasting construction will affect the mechanical response law of foundation pit supporting structure, which is related to the safety and stability of foundation pit engineering. The numerical simulation research method and finite element software ANSYS/LS-DYNA were used to establish a three-dimensional foundation pit excavation model based on the relevant parameters of the second phase foundation pit excavation project of Qingdao Qilu Hospital. By adjusting the blasting interval of each gun hole, the dynamic mechanical laws of rock breakage and support structure during blasting construction of rock foundation pit under different differential conditions were analyzed. The results show that when there is a slight difference in explosive initiation, the crack length in the rock around the gun hole is more developed, and the area of the crushing zone in the rock mass is also increased. Compared with non-differential blasting, the effective stress and vibration velocity curves measured on the pile show more scattered wave characteristics, and there are multiple groups of wave peaks, and the superposition effect of stress waves is not formed. Differential blasting can effectively improve the rock breaking effect and reduce the effect of blasting vibration on steel pipe column.