Compared the sensitivity characteristics and standing wave ratio of the symmetric semicircle dipole and asymmetric semicircle dipole semicircle inner sensors, figure 3 shows the sensitivity graph of the two sensors, figure 4 is the standing wave ratio characteristic of the two sensors. It can be seen from the figure 3 that the coupling characteristics and coupling frequencies of the symmetrical semicircle dipole sensor are more accord with the GIS internal wave spectrum characteristics of partial discharge. From figure 4,it can be seen that the start frequency which the value less than 2 of the standing wave ratio curve of the symmetrical dipole is lower than that of the asymmetric dipole.