Abstract: An on-line surface defect inspection system for cold rolled strips is introduced. The system is equipped with CCD matrix cameras to capture images of steel surface simultaneously. A parallel computer system is used for image processing to obtain defect information on steel surface. The system is specialized in software designing for real-time data processing. With samples from industry, the system is tested that six types of surface defects of cold rolled strips can be detected and classified with high rate, including ‘emulsion marks’, ‘rusts’, ‘scales’, ‘roll imprints’, ‘coil breaks’ and ‘edge cracks’.The recognition rate of the system for these six kinds of defects is more than 90%.