Abstract: A biodegradable composite film was prepared using whole marine biological resources in this study, with sodium alginate (SA) being employed as the film-forming substrate, TEMPO-oxidized brown algal nanocellulose (TOCN) as the fortifying agent, and chitosan (CS) as the bacteriostatic agent. CS/TOCN/SA composite films were prepared by solution casting, and the optimal composition of the SA matrix membrane was obtained by response surface method. The effect of TOCN on the mechanical properties and barrier properties of the composite films was investigated. Results showed that, when the TOCN mass fraction was 3% (accounting for SA dry mass), the tensile strength of the film was increased to 211.90 MPa, and the elongation at break was improved to 38.6%. The addition of TOCN was also observed to reduce the water vapor transmittance from 0.45±0.03 g·mm/(m²·h·kPa) to 0.30±0.01 g·mm/(m²·h·kPa) and oxygen transmittance from 4.63±0.12 mg/(m²·d) to 3.09±0.2 mg/(m²·d). When 16 mg/mL CS was incorporated into the TOCN-enhanced SA membrane with a mass fraction of 8% (accounting for SA dry mass), the composite membrane was found to exhibit a significant inhibitory effect on Shewanella putrefaciens. Compared with the matrix membrane, the composite membrane packaging of Litopenaeus vannamei was demonstrated to effectively delay the lipid oxidation of the product (16.8%), inhibit the increase of TVB-N value (18.9%), and control the growth and reproduction of microorganisms (7.4% reduction in total bacterial count) after 4 days of storage at 4 ℃. Additionally, the composite membrane was shown to significantly inhibit the polyphenol oxidase-promoted browning reaction (3.5%) of the shrimp. The results indicated that the CS-TOCN synergistically strengthened SA composite membrane possessed a good fresh-keeping effect on Litopenaeus vannamei, and had potential application value in the quality preservation of chilled and fresh aquatic products.