Abstract: Nano-cellulose (NCC) was used as raw material to prepare oxidized nanocellulose (TONC) by TEMPO reagent, and then TONC reacted with fatty amines that had different chain lengths under the action of catalyst to obtain fatty amine modified nanocellulose, which were prepared from octadecylamine (OCA) and named as DOATONC, TEATONC, HEATONC and OCATONC prepared from dodecylamine (DOA), tetradecylamine (TEA), hexadecylamine (HEA), respectively. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and elemental analysis showed that the aliphatic chain was successfully grafted, and the crystal form. of the modified nanocellulose did not change, which was the original type I crystal form. The angular and dispersibility tests showed that the hydrophilicity of the surface of the modified nanocellulose decreased significantly with the increase of the aliphatic chain length associated with the increment of contact angle from 65.8° to 93.9°. The dispersion decreased first and then increased, which was reflected by that the dispersion rate was 25.17% first fell to 11.97% and then rose to 71.71%. The composite membrane was prepared by adding 1% modified nanocellulose to polylactic acid (PLA). The mechanical properties test results showed that the mechanical properties of the composite membrane were significantly improved with the increase of fat chain, among which tensile strength and elongation at break of PLA/OCATONC composite membrane reached 40.2 MPa and 6.39%, respectively.