Films with specific performance, such as membranes for lithium ion battery separator, films for packaging or capacitor film, are mostly produced by stretch processing of semi-crystalline polymers, during which mechanical deformation and temperature reconstruct structures like lamellar stacks and spherulite of precursor films. The interplay between hierarchic structures and external fields presents a grand challenge on film processing. In this work, we study the intrinsic deformation mechanism of lamellar stacks, during which isotactic polypropylene (iPP) and high density polyethylene (HDPE) precursor films composing of highly oriented lamellar stacks are taken as model samples. With a combination of home-made uniaxial stretching machine and in-situ synchrotron small- and wide- angle X-ray scattering (SAXS, WAXD) measurements, stretch-induced structural evolution of the oriented lamellar stacks in iPP and HDPE films is studied at different temperatures. The critical strains of structural transformations, such as cavitation, long period, orientation parameter, crystalline, fibrils, are extracted out, which are closely related to non-linear mechanical behaviors like plastic deformation, yield, strain hardening and etc. Based on structural evolution at different temperature, we constructed a morphology diagram in strain-temperature space. Three regions with different deformation mechanisms are defined in different temperature ranges, where destruction of amorphous, crystal slip, and melting and crystallization play dominant role in yield, respectively.