Abstract: Line-scan CCD cameras were used as surface image acquisition devices for hot-rolled strips to avoid problems produced by surface inspection systems based on area-scan CCD cameras. Linear laser was used as the illumination device for homogeneous illumination from long distance under the environment of high temperature. The precision of image acquisition could be higher than 0.5 mm with line-scan CCD cameras and linear laser. A new concept of defect detection was proposed to avoid the disturbance of scales, water and un-homogeneous illumination on the surface of hot-rolled strips. Different detection algorithms were developed for different types of defects. Up to now, detection algorithms for longitudinal cracks and edge cracks were developed, and the detection rate were higher than 95%.