The utility model relates to an extra-high-tension cable on-line partial discharge monitoring system, which comprises an electromagnetic-coupling partial discharge on-line detection device, a capacitive coupling partial discharger and an on-line partial discharge detection device, wherein the on-line partial discharge detection device is connected with the electromagnetic coupling partial discharge on-line detection device and the capacitive coupling partial discharger. Compared with the prior art, the utility model has the advantages that the fingerprint information of the partial discharge signal magnitude-frequency characteristic and signal characteristic statistic evolution are set up, and the key characteristic quantity of the partial discharge signal is first researched in the world. The utility model aims to realize the technical innovation of mathematical algorithm and achieves the major breakthrough of the partial discharge identification technology and the on-line detection testing technology on the basis of the technology innovation of partial discharge signal characteristic analysis.