Abstract: The methods of world-wide sheet shape control of hot rolled strip steel,i.e.hydraulic roll bending,roll cross sliding four-high mills (HCW,CVC,etc.) and PC+ORG mills and the technologies of sheet shape on-line determination and on-line control are reviewed.An investigation is conducted on the inherent imperfection of traditional four-high hot rolling mills.The optimum plan is proposed to reform traditional rolling mills.The suggestions are put forward for Panzhihua I.& S.Co.to adopt this technology.