In order to solve the problem of edge delamination during slitting and trimming of 09CrCuSb acid resistant steel hot rolled coil, three typical edge defects of 09CrCuSb hot rolled coil, namely edge delamination, side bulge on the edge end and longitudinal crack on the edge end parallel to the rolling direction are studied by metallographic microscope and SEM-EDS analyzer. The results show that the edge delamination defects are actually caused by hot rolled side guide extrusion, and do not occur again after correcting the side guide position. The key to determine the cause of edge delamination defects lies in the inner surface state of delamination defects. The side bulge is due to the edge and corner crack of the slab caused by the accuracy deviation of the continuous caster. The deviation of the arc alignment and roll gap of the continuous caster is controlled within 0.5 mm, and the defect incidence is reduced from 5.4% to less than 0.2%. The side bulge defect is actually the initial form of hot rolling roll edge. The longitudinal crack on the edge end is due to the cluster bubbles on the narrow edge of the continuous casting slab and the strong crack sensitivity of the steel itself. By reducing the argon of the continuous casting stopper and nozzle to 4-6 L/min and controlling the crack sensitive elements according to the standard lower limit, the defect occurrence rate is reduced from 8.7% to 0.45%. It provides a reference for controlling the defects of 09CrCuSb hot rolling coil.