Using Camellia oleifera shell as the research object, the cellulose was extracted by alkali boiling and bleaching method and the TEMPO oxidized cellulose nanofibers TOCNs was prepared by TEMPO (2, 2, 6, 6-tetramethylpiperidine-1-oxyl radical) oxidation. The semi-interpenetrating cross-linking network between oxidized nanocellulose and SA (sodium alginate) was established by ionic cross-linking method to produce a composite film with excellent comprehensive performance. The composite films were tested for structure, mechanical properties, thermal stability and oxygen barrier properties. The results show that that TOCN/SA films had smooth surface and dense internal layered structure, and good compatibility of the proper amount of SA with TOCNs. When the mass fraction of sodium alginate increased to 42%, the strain at break of TOCN/SA film increased by 138.6%, the oxygen permeability decreased by 15.55%, and the carbon residual content increased by 21.4%, which indicates that TOCN/SA composite film has good mechanical properties and thermal stability, and maintains good oxygen resistance as well.