Abstract: The objective of the paper is to analyze the affecting factors of spalling, which is one of the typical damage that occurs on the backup rolls of a roughing mill during stainless steel rolling process of 2250mm hot strip mill. Based on the theoretical study and fracture analysis on spall, the peak value of the uneven contact pressure between the work roll and the backup roll is found to be the key factor for the spalling accident during rolling process, which is caused by arduous operating conditions of the largest stainless steel production lines in the world. The three-dimensional finite element models of 4-high roll stacks are developed with measured work and backup roll contours configurations in service. The analysis based on the models demonstrates that the peak value of contact pressure and the location of the peak are influenced by strip width, unit width rolling force and work & backup roll wear contours in different service period. The simulation results show: (1) the peak value of the contact pressure between rolls increases sharply with the increasing of the strip width and unit width rolling force; (2) the peak and the dissymmetry of the roll contact pressure become larger when the work rolls and backup rolls are at the end of the service; (3) the location of the peak shows good agreement with the actual position of spall at the edge of backup rolls. The developed backup rolls have been successfully applied to the production mill without spalling by strip rolling of 6 millions tonnage and more.