The work aims to investigate the effect of polyols as plasticizers on the properties of starch-chitosan films, evaluate the plasticizing effect of four polyols and select the best one. Four kinds of polyols were used as plasticizers to prepare chitosan-starch films by tape casting. The influence of plasticizer content on the mechanical properties of the ma-terials was analyzed. The structure and properties of the composite films were characterized by SEM, FTIR, X-ray Diffraction and static contact angle. Polyols were added to starch-chitosan solution as a single plasticizer. The maximum value of TS was 53.39 MPa when 15% mannitol was added, and the maximum value of EB was 45.11% when 60% glycerol was added. When the glycerol content was 50%, the comprehensive effect was better with TS value of 21.36 mpa and EB value of 35.33%. The starch and chitosan have good compatibility in the composite membrane. The addition of plasticizer is beneficial to promoting the plasticization of starch and improving the mechanical properties of the composite film. For the plasticizer in the low or medium concentration range, there is not effective plasticizing effect. Glycerol has the better effect among the four kinds of polyol plasticizers.