In the recent years, due to environmental challenges and non-renewability of fossil sources, synthetic polymers in many applications have been replaced by biopolymers. Whitin the wide family of biopolymers , the starch has the high usage in various domains such as food packaging industry applications, because of its availability, biodegradability, and biocompatibility. Chitin is one of the most common biopolymers used as filler and reinforcement agentes in the preparation of nanocomposites. The aim of this study is extraction and characterization of chitin nanofibers from Mucor indicus and investigation of their effect on starch based biocomposites . First M.indicus was grown in a liquid medium. The purpose of this part of the study was to evaluate the effect of liquid medium composition and to produce maximum chitin content. The results of tests showed that the maximum chitin was obtained in the presence of 2.5 g/l phosphoric acid as phosphate source, 2.5 g/l of potassium hydroxide as potassium source, and 1 g/l of yeast extract. After separation of chitin fibers, a mechanical proce were used for producing chitin nanofibers. During the chemical extraction process , in the first step lipids, proteins, and carbohydrates soluble in alkali solution were removed with alkali washing of the biomass and the alkali insoluble materials was produced. In the next step, removal of phosphate was carried out. After sulfuric acid hydrolysis, cell wall analysis showed that phosphate was less than 1% i the cell wall . Finally chitosan was eliminated by lactic acid and then decolorization was done. At the end of this two-step, cell wall analysis showed that the extracted material contained 85% chitin, small amounts of chitosan, and is free of phosphate. The FT-IR results showed that different materials in various stages of extraction were removed successfully. The average width of 28 nm was obtained for nanofibers from SEM images. X-ray diffraction results showed that crystallinity index of nanofibers was 82%. In order to produce nanocomposites, starch (5 g) dissolved in water (100 ml) and then the solution was well mixed with of 5, 7, 10% of chitin nanofibers, and then nanocomposites were prepared. The results obtained from the mechanical tests demonstrated that a significant increase in tensile strength and modulus of the nanocomposite films were found in 5% chitin nanofibers. When chitin nanofibers were changed from 0 to 10% , elongation at break was decreased from 107% to 48% . Moisture absorption test revealed that the final moisture absorption of nanocomposite was reduced from 51% to 38% when chitin nanofibers were increased from 0 to 5%. The results of traarency test showed that the addition of nanofibers reduces the traarency of nanocomposite films .The traarency index for nanocomposite films with 3, 5, 7, and 10% of nanofiber was 2.15, 3.14, 3.5, and 3.82, respectively. Keywords : Mucor indicus , Optimization, Chitin nanofiber, Starch, Bionanocomposites