Abstract: The oxidized cellulose nanofibrils reinforcing regenerated cellulose (TOCNs/RC) all-cellulose composite films were prepared with 2,2,6,6-tetramethylpiperidinooxy (TEMPO) oxidized cellulose nanofibrils of pine powder as the reinforcments and RC of α-cellulose powder as the matrix by the sol-gel method. The properties of mechanical, optical, oxygen barrier, thermal stability of TOCNs/RC all-cellulose composite films with different mass ratios of TOCNs to RC were investigated. The structure, morphology of TOCNs/RC all-cellulose composite films and the rheology of cellulose solution were characterized by FTIR, SEM, TEM, XRD and rheometer. The results show that TOCNs have significant effects on the mechanical properties of TOCNs/RC all-cellulose composite films. The tensile strength and fracture energy of TOCNs/RC all-cellulose composite films reach at 134.3 MPa and 21.51 MJ·m⁻³ respectively with TOCNs content of 1.0% (mass ratio to cellulose matrix ) , which has the best comprehensive mechanical properties. The transmittance decreases and haze increases as the augment of the mass ratios of TOCNs, but TOCNs/RC all-cellulose composite films still maintain high transmittance (>85%) and low haze (<14%). The TOCNs/RC all-cellulose composite films also have excellent oxygen barrier property and the oxygen transmission coefficient reaches a minimum of 1.47×10⁻¹⁷cm³·cm/cm²·s·Pa at 1.6% TOCNs. The TOCNs/RC all-cellulose composite films have better tensile strength and oxygen barrier property than general plastic films and also have comparable transparency, which can be used as the strength or barrier layer for the flexible packaging composites and have profound application prospects in the field of green and high-performance packaging meterials.