Abstract: The cotton linters was used as raw materials to prepare water-soluble cellulose acetate (WSCA) with high degree of polymerization (D_p=650-680), by high mechanical strength and low degree of substitution novel one-step method. Subsequently, the WSCA solution and chitosan (CS) solution were mixed with different mass ratios to prepare the WSCA/CS composite films. The properties of the composite films were analyzed by SEM, TG, FT-IR, XRD, and tensile tests, and the effects of different mass ratios of WSCA and CS on the microstructure and properties of the composite film were discussed. The results showed that WSCA and CS with different mass ratios could be well dissolved in acetic acid solution and mixed evenly. As the ratio of WSCA increased, the WSCA/CS composite films presented a nacre-like layered microstructure, the nacre-like layered microstructure significantly improved the mechanical properties of the composite film. When m(WSCA):m(CS) was 1:1, the tensile strength of the composite film reached 126.5 MPa and the tensile strain at break was 7.3%, the thermal stability of the composite film was the best, and the maximum thermal weight loss rate temperature was 300 ℃.