The variable gauge rolling process is a new technology designed to produce flat products of different thicknesses such as longitudinal profile (LP) plates and tailor rolled blanks (TRB), which are used in bridge building, shipbuilding, and automobile manufacturing, etc., to decrease the weight and the welding times, etc. In this paper, a series of numerical studies on the wave motion of rolling force in variable gauge rolling (in three stages: down rolling, flat rolling, and upper rolling) were carried out using the finite element method to obtain the deformation of the work piece at different stages of rolling. The rolling force and its wave motion during rolling were analyzed under a variety of reduction ratios, including the coefficient of friction, initial thickness of the plates, and diameters of the rolls. The rolling force obviously increases as the reduction in the down rolling process increases, and then decreases during upper rolling. The rolling force consists of two abrupt wave motions in the transitional zones during the down to flat rolling stage, and the flat to upper rolling stage. These results are significant with regards to precisely controlling the deformation of workpiece in the transition zone during variable gauge rolling.