Open cell foamed plastics have better energy absorption characteristics and better cushioning properties so that they are extensively used in engineering areas. Thus, their visco-elastic behavior has attracted the most people attentions. Based on the Lederman model, the stress relaxation of open-cell foamedplastics was investigated by using the model of standard linear solid to consider the visco-elastic behavior of matrix. The effect of strain loading, structuralparameter and Poisson’s ratio on the stress relaxation curve of open-cell foamed plastics was discussed at the same time. The results show that the stress relaxation curves are not sensitive to Poisson’s ratio and the increase of strain loading or relative density will make the stress relaxation more significant. However, the ratio of initial and final value for stress response does not change with the increase of strain loading. All the above conclusions obtained are very important for overall understanding the mechanical behavior of open cell foamed plastics.