To manufacturing a plastic film, it is important to set the extrusion condition properly since it effects to the appearance and mechanical properties of film greatly. In other words, it is directly related to quality of products. Although the extrusion condition is necessary factor to optimize manufacturing process, there are few investigations which is focused on the relationship between extrusion condition, mechanical properties and inner structure of film. In this research, we investigated the relationship of these three parameters. In detailed, we repelletized LLDPE virgin pellet with twin-screw extruder by different extrusion condition and made thin film with press moulding machine. After that observed the mechanical properties separately. In terms of extruder, we used the twin-screw extruder which is designed for improving mechanical properties of LLDPE pellets after repelletizing treatment. The results of tensile test showed that after repelletizing treatment, the mechanical properties were increased compared with virgin LLDPE film. From these results, Inner structure of LLDPE films which were obtained prominent character by tensile test were analysed by analytical instruments such as Rheometer, XRD, Imaging IR, AFM and SAXS.