Abstract: Described are the main type and characteristic of the steel pipe inside-descaling system, especially the application of the system on a cross rolling expanding mill. The equipment composition, production procedure, working functions and key points of design of the steel pipe inside-descaling system in a hot rolling line are. highlighted.The practical application shows that the descaling system features good descaling effect with stable equipment running, which plays a important role in improving the inside surface quality of steel pipes.