Analysis of the field monitoring signal indicates that the coupling vibration phenomenon of torsional vibration and vertical vibration has existed in the hot rolling mill, and the vibration characteristics are influenced by the effect of double power. A piecewise nonlinear dynamic model has been established for the top working roll of the hot rolling mill. Simulation research using MATLAB proves that the main drive system′s torsional vibration and hydraulic screwdown system vibration can be transmitted to the working roll and affect the vibration characteristics. The phase change angle between the rolling force fluctuation and the torque fluctuation will lead to great changes in the horizontal and vertical vibrations. When the amplitude of the rolling force and motor torque fluctuation are changed, the roller′s vibration shows characteristics of bifurcation and chaos. When external incentives amplitude are changed, rollers exhibit different vibration states, such as period, doubling period, chaos and so on. The results of the simulation and actual measurements are identical, proving that the hot strip mill work roll piecewise nonlinear dynamic model is correct.