This research is a numerical study of the effect of the constrained groove pressing (CGP) process and its impact on a thermoplastic polymer (polyamide PA 66). A simulation is performed using a finite element tool. The effect of the process conditions and the tool geometry on the mechanical properties is noted. The results are significant, the equivalent strain and Von Moses stress have been progressed accordingly to the number of cycles and the tool geometry. Concluding remarks on the alteration of the microstructure have been proclaimed at the end of this paper.