Abstract: To solve the problem of local exfoliation of rolls due to the overstress in the middle of a roll during rolling, the influence function method which a domestic steel plant have used to determine the parameters of a four-high mill so as to analyze its rolls' deformation is introduced in the investigation on the influence of different parameters on the stress distribution along roll axes, such as the diameters and crowns of both back-up and working rolls and the crown and width of workpiece. The results revealed that the changes in roll diameter and crown/width of workpiece have no obvious influence on the stress distribution. However, the change in crown of the back-up roll especially of the working roll affects greatly the stress distribution, which is the main cause for the edge exfoliation of rolls.