The invention relates to a wideband online measuring system for corona current of a high-voltage transmission line, belonging to the technical field of high-voltage testing devices and measurement. The system comprises a remote unit, a local unit and a terminal computer, wherein the remote unit is used for acquiring the corona current I of the high-voltage transmission line, conducting analog-to-digital conversion to the corona current I to obtain a digital signal and transmitting the digital signal to the local unit through radio wave; the local unit is used for receiving the digital signal of the remote unit and transmitting the digital signal to the terminal computer; and the terminal computer is used for receiving the digital signal of the local unit, displaying and storing the waveform of the corona current of the high-voltage transmission line, and completing data storage and analysis. The measuring system can measure the corona current of a AC or DC line on line at high voltage; and since the wireless data transmission is adopted, no external insulation problem exists and the measuring system can run on line for long period in a hostile natural environment and an electromagnetic environment. The invention provides a reliable means for the deep analysis of the corona of the transmission line.