The invention relates to a GIS partial discharge signal propagation characteristic testing system. The system is characterized in that the system comprises a symmetric conical coaxial cavity (3); the top and bottom of the symmetric conical coaxial cavity (3) are respectively provided with an upper signal leading-out head (2) and a lower signal leading-out head in a fixed manner; the interior of the symmetric conical coaxial cavity (3) is fixedly provided with a guide rod (5); the top of the guide rod (5) is electrically connected with a picosecond-level partial discharge signal generator (1) through the upper signal leading-out head (2); the bottom of the guide rod (5) is grounded through the lower signal leading-out head; a side wall of the symmetric conical coaxial cavity (3) is also fixedly provided with at least two central signal leading-out heads; the other ends of the central signal leading-out heads are connected with different input ends of a high-speed oscilloscope (4). The system is simple in structure, is convenient and practical, and can provide reliable and accurate test data for the partial discharge detection and analysis in GIS.