The photostabilization and photodegradation of polyolefins like as a polypropylene (PP), polyethylene (PE) and their E-P copolymer EPT 30U and EPT 30R films were investigated by addition of three different stabilizers and 1 nanoparticle. In the present study, we used three different stabilizers were Chimassob944 (C), Irgafos68 (Ir) and Tinuvin770 (T) and one nanoparticle was multiwalled carbon nanotubes (MWCnts) with different weight concentration (0.1wt%, 0.2wt% and 0.5wt%) for investigated. The main motive of this research was stabilization of polyolefin films. In the present research, the photoirradiation of polymer composite films were studied under accelerated weathering condition (UV radiation λ ≥ 290nm) at 60℃ for different time intervals. The resulting photodegradation of polymer composite films were estimated by optical microscopy and Fourier transform infrared spectroscopy. The increase of carbonyl and hydroxyl functional group during oxidation was evaluated by FTIR spectroscopy. The morphological changes of polymer composite films were evaluated by optical microscopy. It was observed that extent of photodegradation was reduced in all irradiation stabilized polymer composite films, but polyethylene sample containing 0.5wt% Chimassorb944 (C) showed best stabilization as compared to the rest.