With in situ synchrotron radiation X-ray scattering, the structural alteration of polyethylene-plasticizer film during uniaxial stretching is studied at temperature far below melting point of crystal. By analyzing the evolution rule of structural parameters quantitatively, stretch-induced melting and recrystallization process is validated to be the underlying mechanism of plastic deformation for the system. The physical essence of stretch-induced melting is proved to be phase transition driven by elastic energy which originates from lattice deformation. Conversely, the recrystallization process is proved to be controlled by temperature; furthermore, the growth of lamellae during recrystallization is in perfect accordance with kinetic theory by Lauritzen and Hoffman. This study provides a quantitative understanding to the long-existing melting-recrystallization model from a thermodynamics point of view. (c) 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1521-1528