Physical and optical properties of a series of TAC films with different molecular weight synthesized by acetylation of cotton linter have been investigated. The synthesized TACs had fully acetylated structure in which acetic acid contents was about 62%. Dimensional stability, thermal stability, modulus, tensile strength and elongation at break of TAC film were influenced by the molecular weight of base resin and they increased with the molecular weight. TAC films had good transparency as well as optical isotropy. Especially, optical property and moderate physical properties for protective film application in LCD were achieved above the molecular weight of 250kg/mol.