In order to get the nature of the ferroelectric relaxor behavior, the structural changes of electron irradiated of P (VDF-TrFE) copolymer have been investigated through IR spectra, X-ray, DSC, and AFM. The irreversible transformation from the ferroelectric copolymer to the relaxor state induced by irradiation is related to the creation of polar clusters, consisting of a variety of short range coherence of trans-conformation, stabilized by random fields of C=C and C=O bonds. And the existence of nanometer scale crystals embedded in an amorphous matrix may be the base of the relaxor behavior and high performance in these polymers.