Abstract: The nonlinear character of a rub rotor system with SFD is analyzed in this paper.It was found that with an increase in the rotating speed,the amplitude of the system response increases in the end.In such a process,the max amplitude of the system response several kinds of changes.Sometimes it increases,sometimes it decreases,and sometimes it keeps constant.It also was found that there is close relationship between the period solution bifurcation and the max amplitude of the system.At the bifurcation point,the max amplitude of the system varies intensely.SFD has an obvious absorber effect of the system.But when the parameter of SFD exceeds a certain value,the variation of this parameter hasn’t any obvious infection on the absorber effect of the system.And the friction coefficient of the rub has a good effect on the absorber effect of the system too.A large friction coefficient can make the system to work more steadily.But sometimes,a smaller friction coefficient can play a positive role for the absorber to.An imbalance coefficient influences the max amplitude of the system greatly.The higher the coefficient is,the larger the max ampiltude of the system.It also was found that keeping the system under period solution state can make the max amplitude decreasing.