Based on the Hertz contact theory, the model for the transverse impact vibration of a roll with symmetric clearance was established, and the time domain waveform, picture diagram, poincare map of the system were analysed under the conditions of different roll speed and rolling content, different clearance and guide installation stiffness by using the 4th and 5th order RungeKutta method. The nonlinear vibration characteristics of the roll and plate were investigated. The results show that: when the frequency ratio Ω=3, gap d=0.04 mm, nondimensional parameter T=13, and guide installation stiffness k 2=8×104 N/mm, the system state transforms from vibroimpact into viscous vibration. The rolling content and clearance have larger effects on the nonlinearity of system. The larger the rolling content and clearance, the more obvious of the system viscous movement； the roll speed and guide installation stiffness have weaker effects on the nonlinearity of system；The system is always in chaotic motion state in the adjustable ranges of parameters.