Today, from the point of view of environmentally concerns, the nanocomposites of PLA are from great interest among the manufacturers of food packaging plastics. Among the all types of PLA nanocomposites, the ones including the oxide of semi-conductive materials such as TiO₂, have attracted the attention of many research centers and industries. Although there seems to be a great interest about producting the nanocomposite of PLA and TiO₂ nanoparticles, but aggregation of TiO₂ nanoparticles in an organic matrix like PLA, makes it difficult to reach a homogenous film with good properties. In this study first, PLA chains were grafted onto TiO₂ nanoparticles surface via reactive melt mixing using a novel approach in presence of SnCl₂ as catalyst. PLA grafted chains were characterized on the TiO₂ nanoparticles using FTIR and TGA analysis, and the optimum ratio of TiO₂ nanoparticles to SnCl₂ in order to abtain the highest amount of grafting, was determined 7.5. Then, PLA-grafted-TiO₂/PLA nanocomposite films, were produced using a twin screw extruder. The microstructure of the nanocomposite films was characterized using SEM and EDAX techniques, and this way, it was observed that the dispersion state of TiO₂ nanoparticles has been greatly improved after modifying TiO₂ surface. Finally, the nanocomposite films were put under UV irradiation(360-420 nm), for 2 months and the weight loss of the films was followed during this period. The nanocomposite films containing modified TiO₂ nanoparticles, showed higher amount of weight loss in comparison with the film containing bare TiO₂ nanoparticles. The nanocomposite films were also used to investigate the antibacterial properties, under UV irradiation for 2 hours, using a combined method of JIS Z2801:2000 and ASTM E2180-07. The nanocomposite films showed high antibacterial properties against E-coli gram negative bacteria, although this amount was lower in case of St.aureous gram positive bacteria.