Abstract: As one of the commonly used tunnel construction methods, blasting excavation has become the main method for the construction of mountain tunnels in China. However, blasting excavation will cause the vibration response of existing structures, affect the normal operation of existing structures, and even lead to the destruction of existing structures. In this paper, the Xinling tunnel underpass water diversion power station is taken as the engineering background. The ANSYS/LS-DYNA finite element software is used to analyze the blasting vibration response law of the Xinlin tunnel under the diversion tunnel, and the reliability of the model is verified by the field measured data. Based on the numerical results, the vibration response of the existing tunnel section is analyzed for different excavation propulsion distances, and the existing tunnel damage limit is proposed to determine the tunnel damage range. For the actual engineering problems, the existing tunnel safety is considered. The operation and guarantee of the stability of the surrounding rock were simulated, and 37 working conditions were simulated, and the optimized blasting scheme was given. It has guiding significance for the construction of Xinlin tunnel and provides some reference for similar undercut engineering.