In this paper, we present an analytic approach for the prediction of roll force to be applicable to the billet rolling process which consists of a series of horizontal stands and vertical stands. The approach is based on the deformation shape and employs the assumption that the deformation homogeneously occurs in three directions. Strain and strain rate are calculated by the geometric relationships between those components and the prescribed deformation functions. By integrating the stress components along the rolling direction, roll force is finally obtained. The prediction accuracy of the proposed model is examined through comparison experimentally mesured roll force with computed ones.