Equal channel angular extrusion (ECAE) is a powerful tool to modify microstructure via high plastic deformation without altering sample geometry. This article investigates the behavior of a polypropylene processed by ECAE. A finite element analysis in which the material constitutive law is coupled with damage by means of Gurson-Tvergaard damage potential allowed to model experimental tests achieved on this material. Such a modeling allows the prediction of the extrusion load, strain and stress fields, and void volume fraction distribution. The need for the use of a back-pressure is highlighted.