A platform is designed that combines CoroCAMⅣ+ with the virtual instrument programming environment Labview 8.0 for evaluating and analyzing the development of corona discharges. With an appropriate algorithm and flowchart for digital image processing， the area percentage of the UV image within the discharging region is defined as the characterizing parameter of quantifying the intensity of corona discharge by processing the UV video of corona discharge recorded in real time. Under the approximate standard atmospheric ambient， a study is made on corona discharge under the power frequency voltage of the rod-plane gap based on the UV digital image processing. The results show that the flowchart of the digital image processing proposed can reproduce the images observed by the UV camera so as to guarantee the validity of the quantifying parameter of corona discharge; the characterizing parameter can distinctly reflect the corona discharge developing stages; the law of the UV imaging of corona discharge attenuating with the observation distance is obtained; the standard conversion method—the criterion for the UV imaging detection of corona discharge is proposed.