Abstract: Abstract: In this paper, the preparation process of nanofibers with oxygen barrier materials was studied and the oxygen barrier effect of cellulose nanocrystals (CNs) coatings on 4 kinds of flexible packaging substrate was compared. The preparation process was as follows: First, the nanocellulose crystal with 1% content was prepared by the method of acid hydrolysis, and then a suitable amount of nanoscale crystal was dissolved in the distilled water by ultrasonic dissolution. When it became clear and transparent, the nanoscale coating solution with a concentration of 8% was obtained. The corresponding composite film was prepared by placing 4 kinds of substrate on a coating machine and the coating liquid was uniformly applied to the surface of the substrate at a coating speed of 2.5 mm/s. The obtained composite film was observed under an atomic force microscope. The results showed that the nanocellulose was evenly coated on 4 kinds of substrate to form a dense composite membrane structure. Moreover, the surface roughness of coated materials was significantly reduced, making it difficult for microorganisms to pollute the membrane. Based on the evaluation of the basic properties of the composite film, it was found that the coefficient of friction on the surface of the coated material was significantly lower than that of the original substrate except the oriented polypropylene (OPP) film, making the resulting composite membrane easier to mass-produce on high-speed packaging machines. The CNs coating method did not improve the optical properties of the composite film very well, and its optical performance was not significantly different from that of the original substrate. Evaluation of the oxygen barrier performance of the composite membrane revealed that CNs coating greatly increased the oxygen barrier properties of the substrate. The oxygen barrier performance of the original basement membrane was greatly improved by the composite film coated with CNs. The oxygen transmission of all composite films decreased by more than 98%, except the composite film made by OPP substrate. The application of the composite membrane on fresh-cut apples showed that the 4 kinds of oxygen-insulating composite membranes could effectively prevent the infiltration of oxygen, which effectively inhibited the decrease of the color of fresh-cut apple slices and the loss of its nutrients. The experimental results also showed that the oxygen isolation effect of oriented polyamide (OPA) film coated with CNs was the best, and the oxygen isolation coefficient was 0.003 cm3·μm/(m2·d·kPa). Compared to PET (polybutylene terephthalate), CELL (celluloid) and OPP film, the oxygen coefficient of OPA film was increased significantly, respectively. The fresh-cut apple was stored for 4 d under the temperature of 3-5 ℃. On the 4th day, compared with the control group, the luminance value of the OPA based oxygen insulating composite membrane was increased by 11.7%, and the contents of titratable acid, vitamin C and soluble solids increased by 105%, 42.6% and 36.2% respectively. This study provides a completely new process for the preparation of oxygen barrier membranes and a new method for preventing browning and preservation of fresh-cut apples.