Abstract: The vortex induced vibration response of a rigid cylinder supported by perfectly plastic nonlinear spring in a fluid flow was simulated for the first time. Wake-oscillator prediction model and 2D CFD method based on loose coupling algorithms were adopted. The results of above two methods all showed that, vibration amplitude jumps to a maximum value when cylinder movement exceeds the nonlinear spring limited displacement,then decreases with velocity increasing. The response peak value for nonlinear spring case is higher than linear spring,but at the lower flow velocity. As the same time,the simulation of CFD presented that vibration frequency for synchronization is close to vortex shedding frequency at the beginning,and then switch to above the natural frequency in still water when the amplitude reaches a peak value.