In the process of blasting excavation of urban subway， the key to ensuring the safety and stability of adjacent viaducts is to analyze the dynamic response characteristics of viaduct structures under blasting vibration. Based on the blasting excavation engineering of subway tie passage between Jiedaokou station and Xiaohongshan station of Wuhan metro line 8， the finite element numerical calculation model is established by software ANSYS/LS-DYNA. Combined with the field monitoring data， the dynamic response characteristics of the viaduct under the blasting excavation of the subway tie passage are analyzed. The results show that there is a negative correlation between the vibration velocity and the distance of the source of the viaduct during the process of the down blasting， and the blasting under the viaduct is the most dangerous condition. Moreover， there is a positive correlation between the peak vibration velocity and displacement of the viaduct piers. Combined with code for seismic design of urban bridges， the control vibration velocity of pier blasting is 4.55 cm/s，which provides guidance for the actual blasting engineering.