At recent years, because of environmental problems and not renewable form of oil resources, natural polymers are replaced artificial polymers in most applications. Among the large family of natural polymers, chitosan due to the affluence, biodegradablity and bio-compatibility was used in different fields such as food packing industry. Chitin is the most usual bio polymers that was used in nano composite synthesizing as reinforcing and filler agent. In the current work, the aim is to extracting and characterizing the chitin nano fibers from shrimp shell and investigating the effect of its addition to chitosan- based bio composites. During the extracting process, first of all, proteins and soluble carbohydrates were alkali washed in sodium hydroxide to be removed from shrimp shell. In the next stage, salts were removed using acid chloric and finally decolorizing and lipid removal were done using acetone and hypochlorite sodium. Result of shrimp shell analyses revealed that material with 88 % chitin, has a little lipid and lacks protein and carbonate calcium. Spectroscopy results of fibers at the different stages determined that removing the matrix materials were done successfully and FT-IR spectrum, confirms this result. Average diameter of nano fibers was calculated about 21 nanometer using Scanning Electron Microscopy. Crystallization of nano fibers were estimated at 84 % using X-ray diffraction results. In order to preparing nano composite, chitosan was dissolved in acetic acid and then was mixed thoroughly with 1, 3, 5, 7 and 10% of chitin nano fibers. To creating transverse joints of chitosan film, adipic acid were used to reveal a comparison between the synthesized films properties. SEM images of fracture surface of chitosan composite film with 5% of chitin nano fibers showed that fibers are distributed uniformly in matrix and there is a good interaction between matrix and nano fibers. Results of mechanical tests proved that ultimate strength and module of nano composite films increases about 43% with increasing in chitin nano fibers up to 5%. Strain in fracture point decreased about 52 percent for films with 0 to 10% nano fibers. Improvement of strain in fracture point was performed using glycerol. In the next step, in order to recovering the ultimate strength and module, adipic acid addition to chitosan films, made physical and chemical transverse joints. Ultimate strength results of chitosan films containing physical and chemical transverse joints in comparison with pure films containing emollient were increased about 224% and 283%, respectively. In this stage, treating with 5Wt-% of chitin nano fibers led to highest strength of 118 MPa. Water absorption test proved that water absorption rate in samples without emollient is significantly higher than other samples. With addition of emollient and firing films, water absorption rate decreases. Traarency test showed that adding nano fiber and glycerol emollient results in traarency decreasing for nano composite films. Key wor ds: Shrimp shell, Chitin nanofibers, Chitosan, Bionanocomposite film, Biodegradable polymer