Abstract: Nanocrystalline cellulose (NCC ) was isolated from cotton via sulfuric acid hydrolysis. The calcium alginate/nanocrystalline cellulose composite films were prepared by solution casting. The properties of mechanical, water sorption, water vapor permeability (WVP) and light transmittance were studied. The result showed that the diameter of NCC determined based on TEM was 20⁴0nm and the aspect ratio was 7. With increase of NCC content, the tensile strength (TS) and breaking elongation (E) values increased significantly, however, the water sorption, WVP and light transmittance values decreased significantly.