Abstract: Aiming at the problem of inaccurate thickness measurement caused by insufficient detection accuracy of cable insulation edge in current automated equipment, a insulation edge detection method based on Closed-Form matting algorithm was proposed. Regarding insulating part in imaging as foreground pixels and gasket part as background pixels, imposing certain constraints on imaging, opacity of unknown pixels through Closed-Form matting algorithm was estimated, accurate extraction of insulation pixels was achieved, finally insulation thickness of cables was measured. Simulation and experimental results showed that the proposed method could effectively extract cable insulation edges and improve measurement accuracy of insulation thickness.