Abstract: Through the analysis on the rub characters between rolls of 4-high strip mill, the co-operation of small convexes between the backup and work roll is discussed. The axial displacement models are established on the touching surface between the rolls and between the work roll and rolling piece. With the predisplacement theory, the effect of the surface roughness of rolls, resistance to deformation and viscosity of rolling piece on axial force of rolls is analyzed. The theory formulas for axial force of the roll system of rolling sheep mills are obtained under the condition of symmetry rolling, and more complex axial force of work rolls is discussed. The axial force theory has been verified.