Abstract: Taking the vertical rolling roller and its double row tapered roller supporting bearing as the research object, a mechanical model for calculating the supporting force of bearing is constructed through mechanical analysis. By analyzing the contact force and local deformation of bearing roller, a calculation method for load distribution and fatigue life of bearing under composite load is established. Taking a specific supporting bearing of the vertical rolling mill as an example, the displacement curves of the bearing axis and the force on the rolling element are systematically discussed. On this basis, coupled calculations are conducted on the deformation of steel slab and the contact force of bearing during vertical rolling process, and the influences of several process parameters on roller stress and bearing life are studied. The research shows that the axis trajectory of the bearing is an irregular ellipse. The contact force between the roller and the inner ring rib of the bearing is very small. The maximum contact stress between the roller and the inner ring is slightly greater than that of roller-outer ring. When the width reduction rate, slab thickness, slab width and vertical roller radius increase, the maximum contact stress of the roller increases, and the fatigue life of the bearing decreases. Among the main rolling parameters, the influence of width reduction rate and slab thickness is more significant. The difference of load value between the two rows increases with the increase of the composite load, which results in the decrease of bearing life.