A method for calculating the flare area based on image segmentation is proposed to study the ultraviolet image characteristics of the wet-contaminated discharge of disk-shaped insulators. First, based on the C-V model, the radial distribution of an ultraviolet image of a disk-shaped insulator is studied. It is then compared with the infrared temperature-field curve to verify its rationality. Finally, the ultraviolet image characteristics of the wet-contaminated insulators with different electrical resistivities and wind speeds are studied. The results show that the C-V model has strong anti-interference performance when applied to image processing, and is suitable for the study of the radial discharge intensity of disk-shaped insulators. The ultraviolet flare area of the insulator increases with a decrease in the surface resistivity. The wind speed has an obvious influence on the discharge intensity of the disk-shaped insulator. The results provide a reference for evaluating the radial discharge intensity of disk-shaped insulators.