Tear (notched) is an important mechanical property of polymer films. However, the actual mechanism of tear is a complex process in plane stress condition. It is almost impossible to carry out an in-situ study of morphology, structure, and orientation development during a highspeed tear process, in order to understand the mechanism. In the present work, the tear path of a torn linear low density polyethylene (LLDPE) film was studied using micro-X-ray diffraction (XRD) and small angle X-ray scattering (SAXS). Crystals and amorphous segments become highly orientated very rapidly at initiation. The original crystals, rotated crystals, and the broken-up crystals can be differentiated by SAXS due to their orientation in different directions. Higher crystal and amorphous orientation was observed for LLDPE film after machine direction (MD) tear than after cross direction (CD) tear. This may explain why LLDPE films have lower MD tear strength than that of CD tear. At the end of the tearing path, all crystals are broken up and aligned much like a fiber along the tear path direction.