Abstract: During the commission（handover acceptance）test of long-distance ultra-high voltage cable lines,the highfrequency current coil（HFCT）is installed at the end of the bonding lead in the cross bonding link box and the direct grounding box to detect the PD signal. It is of great importance to know the propagation process of the PD signal for selecting locations of PD sensors. In this paper,the propagation of PD under different connection modes of leading cable and transmission cable metal shield layer is simulated. By using the cable modal domain theory,the PD signal of each conductor in the phase domain is decomposed into coaxial mode signal and earth return mode signal in the modal domain,and then the propagation and attenuation characteristics of the PD signal in the core,shield and modal domain circuits under different connection modes are obtained. The simulation results show that the PD signal measured by HFCT at bonding leads is mainly coaxial mode signal. The partial discharge signal flowing through the lead of the straight through joint is relatively weak,therefore the HFCT should preferably be arranged at the end of the lead of the insulated joint.