Rice straw fibers have been used as reinforcing fillers in different polymers, tow composites were prepared by using polyvinyl alcohol and polystyrene polymers with different ratio of polymers. The pressed samples were subjected to various electron beam irradiation dose. The results indicated that, flexural strength, impact strength and modulus of elasticity increase with increasing the polymer ratio in the mix composition. It was found that the water absorption and thickness swelling percentages of rice straw fiber polystyrene composites decrease with increasing the polystyrene content in the same composition, while its values for rice straw polyvinyl alcohol composites improve. These are attributed to hydrophobic and hydrophilic characteristics of the tow composites. The improvement of physico-mechanical properties of both composites with the increase of electron beam irradiation dose are probably attributed to randomly initiated chain reactions, which started by the reactive centers created by electron beam. These observations were confirmed by IR spectrometer and SEM studies.