The authors have tried to develop a method of simulation for analyzing the mechanical behavior of the highly compressible soft materials, most of which are composed of fibers and vacant spaces occupying almost all the volume. First of all, they have measured the stress-strain curve and Poisson's ratio, and have got the constitutive equation. And then, they have developed an approximate approach where the non-linear constitutive equation is linearized based upon the concept of the equivalent Young's modulas. The comparison of the experiment and simulation showed fairly good coincidence, and therefore, it is possible to carry out the simulation of compression of highly compressible soft materials by the proposed method.