: Polyolefins have significantly obtained a main position in packaging industry because of their low cost, light weight, required properties, and low-energy consumption during their processing. To overcome this problem, production of degradable and biodegradable polyethylene is necessary. Starch is a widely used polymer in thermoplastic applications because of its biodegradability. Cellulose is the most available biopolymer on earth occurring in wood and other lignocellulosic sources which can be isolated as nanofibers to reinforce composites. The main challenges in using CNF are associated with the high polarity of cellulose which reduce the usage of nonpolar polymeric matrix. Consequently, CNF modification is essential in order to limit this phenomenum and open new applications by creating compatibility with poly ethylene matrice. In this study, Cellulose nanofibers were isolated from wheat straw by a chemical-mechanical procedure the morphology and size distribution of nanofibers were characterized using FE-SEM. The average diameter and aspect ratio of nanofibers were obtained to be 27 nm and about 45-65, respectively. The free radical polymerization of methyl methacrylate and butyl acrylate monomers was separately done at the presence of cellulose nanofibers by using cerium ammonium nitrate as initiator. It is necessary to mention that the optimum temperature, monomer concentration, initiator concentration and time for polymerization are respectively 35°C, 40 mmol / gr CNF, 2 mmol / dm 3 and 120 min. Also cellulose nanofiber was acetylated by acetic anhydride. Maximum grafting efficiency of 96.5 % was observed for poly (methyl methacrylate) based on the results of gravimetric and XPS analysises on the modified nanofibers. Successful grafting on the cellulose nanofibers surface was confirmed by TOF-SIMS analysis. TGA thermal analysis of nanofibers before and after modification showed that thermal degradation increased 40 °C and 20 °C respectively for modified nanofiber by polymer brush and acetylated nanofibers compared to the unmodified nanofibers. XRD analysis was performed after surface modification to determine the amount of crystallinity. Modified nanofibers with poly (butyl acrylate) and poly (methyl methacrylate) respectively showed 77 % and 54 % lower crystallinity compared to unmodified nanofiber. Most hydrophobicity after surface modification was observed for poly (methyl methacrylate) grafted nanofibers with contact angle of 100.15 ? . These mentioned properties are highly suitable for using cellulosic nanofibers and modified cellulose nanofibers in polymeric nanocomposites. In this research, the effect of bio nanofibers on physical and mechanical properties of polyethylene/starch/polyethylene grafted maleic anhydride blend was investigated. Nanocomposites reinforced with different amounts of CNF and modified CNF from 1 to 5% were prepared using a twin screw extruder. To evaluate the mechanical performance of nanocomposites, tensile properties were measured. It was observed that by increasing modified CNF content tensile strength, Young’s modulus and elongation at break were was increased compared to CNF nanocomposite. In addition, water absorption and degradability under soil was decreased with adding modified CNF in nanocomposites. Key words: Wheat straw, Cellulose nanofibers, Total crystallinity index, optimizing, nanocomposite, degradability.