Abstract: To explor the enhanced effect of nanocrystalline cellulose( NCC) in alginate- starch based composite films.NCC was prepared from degreasing cotton by chemical pre- treatment combine with ultrasonic disruption. The alginate- starch composite films were prepared by solution casting method,using NCC as enhanced component and glycerol as plasticizer. The microstructure observation showed that NCC from degreasing cotton was rod- like with an aspect ratio about 8,and its diameter was about 30 nm. The mechanical properties,barrier properties,optical properties,water solubility,DSC and FTIR of the composite films were tested,the results indicated that 5%( w / w) NCC can efficiently increase the tensile strength,dissolution time and thermal stability of alginate- starch based films,the water vapor permeability coefficient of the composite film with 5%( w/w) NCC was also reduced,besides,5%( w/w) NCC almost didn't affect the transparency of composite films.