Abstract: Theory and basic formula of roll elastic deformation on a 4-h mill were investigated with the influence function analysis introduced and the analysis of roll elastic deformation program made for the simulation of an 1700 mm hot strip mill (HSM) to calculate the roll deformation. The results showed that the increase in roll bending force will decrease the crown of strip at exit, and the change in roll bending force has great influence on the distribution of pressure acted on strip by backup roll and work rolls, work roll deflection and flattening effect due to backup and work rolls, while the influence on backup roll deflection and flattening effect due to strip and work roll is small. There is a peak value of pressure due to both rolls at both ends of the backup roll. All the results mentioned above are in agreement with the theory of rolling process and what happened in the site.