The work aims to synthesize a new polyurethane with hexamethylene diisocyanate (HDI), polycarbonate diol (PCDL) and hexanediol (HDO) to study the effects of R value (molar ratio of isocyanate to hydroxyl group in the whole prepolymerization reaction) on the performance of polyurethane film (PU film). Raw materials with different R values were chemically synthesized by prepolymerization and then cast into a film. The effects of R value on mechanical properties, water contact angle, transparency and oxygen permeability of PU film were analyzed. The PU film was tested and characterized by infrared spectroscopy, differential scanning calorimetry and thermogravimetric analysis. As the R value increased, the mechanical properties and thermal stability of the PU film became better, the water contact angle and microphase separation degree increased, but the transparency and oxygen permeability coefficient decreased. A new type of polyurethane is synthesized with the above-mentioned three raw materials, and the overall performance of the PU film is improved as the R value is increased.