Backup rolls of hot rolling mills have long service life, can withstand harsh working conditions during rolling. However, they undergo severe roll wear that affects the contact force between rolls, resulting in roll fatigue and even spalling accidents. In this study, a fatigue-damage prediction model of a backup roll considering roll wear is proposed. The elastic deformation model of a fast roll system is established using influence function method to calculate the contact stress between rolls. Considering the uneven wear of rolls, a dynamic fatigue-damage prediction model of a backup roll based on the fatigue-damage accumulation theory is established. The model can be used to calculate the wear and fatigue damage caused to a roll after rolling a piece of strip steel. The analysis results show that the proposed model optimized the actual grinding quantity of the backup roll. That is, after optimization, the proportion of secondary grinding is reduced by 35.54%, and the backup-roll consumption is reduced by 8.02%. Therefore, the application of the proposed model can effectively reduce roll consumption, improve grinding efficiency, and provide theoretical support and industrial application reference for the prediction and control of fatigue damage to backup rolls in the field of hot rolling.