Today bio-nano composites of biopolymers are from great interest from the point of view of environmentally friendly concerns. Among all of the biopolymers, poly lactic acid (PLA) has been greatly used by researchers and industrial centers all over the world, due to its properties. In the earlier study, surface modified TiO2 nanoparticles with polylactic acid chains produced by reactive melt-mixing, using internal mixer apparatus in the presence of SnCl2 as catalyst. In this study, nano-composite films of modified-TiO2/PLA in different nanoparticle amounts and optimum amount of catalyst produced by melt extrusion, using twin-screw extruder. The composite film of unmodified-TiO2 nanoparticles in PLA matrix also prepared as reference to compare the results. Scanning electron microscopy (SEM) results showed that modified TiO2 nanoparticles better dispersed in PLA matrix, while unmodified nanoparticles tended to aggregate. Furthermore, the nano-composite films in which produced in higher screw speed, exhibited both better dispersion and distribution in matrix. The produced nano-composite films then, were exposed to UV-visible irradiation in the range of 360-420 cm ̄¹, to study the effect of nanoTiO2 content and the screw speed on UV-degradation rate in both short term and long term degradation tests, and the percentage of films’ weight decrease as a function of time, have been provided as result. It’s been found that, in both short term and long term exposure, the degradation rate of nano-composite films increased by increase in TiO2 content and screw speed. Furthermore, test results showed that SnCl2 has a reducing effect on photo-catalytic effect of TiO2, since it has an absorbance peak in UV-visible spectrum in the range of 360-420 cm ̄¹. The surface of films, both before and after exposure also characterized by scanning electron microscopy.