Abstract: Aiming at the problem of inaccurate thickness measurement caused by insufficient detection accuracy of cable insulation edges in current automated equipment, the insulation edge detection method based on Closed-Form matting algorithm was proposed.This method regards the insulating part in the imaging as the foreground and the gasket part as the background, imposed certain constraints on the imaging, estimated the opacity of unknown pixels through the Closed-Form matting algorithm, and achieved accurate extraction of insulation pixels, ultimately measuring the insulation thickness of the cable. Simulation and experimental results showed that this method can effectively extract the insulation edges of cable and improved accuracy of insulation thickness measurement.