Long-distance urban gas-insulated transmission line（GIL）has many complicated shell structure such as expansion joints and gas basin insulators，which will cause the time delay of vibration signal propagating along the GIL shell，and then affect the positioning accuracy of vibration fault location on-line monitoring system based on time difference method. In order to clarify the influence of GIL complicated shell structure on the propaga? tion process of vibration signal and provide the basis for the improvement of the subsequent GIL breakdown fault loca? tion method，the propagation equation of vibration signal in the fluid and solid field and the coupling relationship be tween the two fields are analyzed theoretically，and the acoustic-structure coupling finite element numerical simula? tion method for the propagation process of vibration signal in GIL is presented in this paper. Then，the propagation characteristics of vibration signal in GIL shell under different excitation modes are studied. The experiment of vibra? tion propagation characteristics of GIL shell is carried out in Nantong 220kV GIL engineering site，and the typical wave velocity and time delay of vibration signal through 220kV GIL expansion joint，gas basin insulator，elbow and support are obtained. At the same time，a finite element simulation model consistent with the experiment condition is also established，which verifies the feasibility and effectiveness of the proposed numerical simulation method for vi? bration signal propagation in GIL. The results show that for the S-wave vibration signals monitored by the vibration fault location on-line monitoring system，the complicated shell structure of 220kV GIL can produce a delay ranging from 0.1ms to 1.1ms.