The utility model discloses a device for detecting the partial discharge of a terminal of an on-site power cable, and the device comprises electrical equipment in a GIS cylindrical substation, wherein a high-voltage cable of an external inlet wire enters into a substation and then is connected through a cable terminal. The ground wires of B-phase and C-phase cable terminals of a loop line are respectively provided with a high-frequency current sensor. Meanwhile, a binding site of the C-phase cable terminal with the GIS is equipped with a super-high-frequency current sensor. The two high-frequency current sensors and the super-high-frequency current sensor are respectively connected to a signal converter, and are connected to a data-collection industry computer through the signal converter. The data-collection industry computer is provided with a waveform oscilloscope, and is portable detection equipment which can achieve the continuous data collection, collects power-frequency reference phase signals, and employs power-frequency phase trigger sampling. The device is simple in structure, is convenient and reliable in application, does not change the structures of a running cable and an accessory, and is suitable for the on-line detection of a power cable which is put into operation.