Abstract: The causes of cracks forming in abrasion- resistant steel plate NM360 after cutting had been investigated by means of metallographic microscope and SEM. Observation shows that there are several segregations in the mid- depth of the plate and network carbide distributes along the grain boundary. The impact of various residual stresses generating during heat treatment quenching cooling and the flame cutting process on this area is the main reason for the formation of the delayed crack. The delayed cracks can be effectively avoided by reducing defects in continuously cast blooms,improving the heat treatment process and preheating the slab and slow cutting.