Fabric compressibility is very important in all RTM processes, and affects both the material and processing properties of the part. As the fabric is compressed by fluid pressure or the mold surface the fibers get compacted and the fiber volume fraction increases. This decreases the thickness of the part, decreases the permeability, and decreases the porosity. Compressibility is possibly more important to understand in one sided molding processes than in closed-mold processes. In this study, changing in permeability for four types of fibers that have been under pressure is measured. Based on experimental data related to permeability changes, for each type of fibers, plotted corresponding curves using interpolation and for each sample, modeled its behavior. Finally, the model outputs for several samples compared with experimental data to evaluate precision of model. The results showed that this model with low error can predict the permeability changes of fibers.