Considering the influences of piecewise symmetrical nonlinear stiffness between rolls of rolling mill and external periodic excitation on rolling mill, a vibration model of mill rolls with piecewise symmetrical nonlinear stiffness was established. Firstly, the piecewise symmetric nonlinear stiffness term was fit into a continuous curve by the least square method to give the dynamic equation of vibration system, and the amplitudefrequency response equation of the system was solved by multiscale method. On this basis, the bifurcation response equation of the mill vibration system with codimension 3 was obtained by the singularity theory, and the steadystate response transition set of the system with three different folding parameters was discussed. Furthermore, the bifurcation characteristics and the conditions of different bifurcation patterns of the vibration system were studied in the case of nonautonomous. Finally, the erosion process of the safety basin for vibration system and the trend and critical value of the system to chaos were studied by numerical simulation, and the bifurcation and chaos behaviors of the safe basin for vibration system were given. The research results provide a theoretical reference for the analysis and control of dynamic behavior which widely exists in the rolling mill vibration system.