Cellulose acetate (CA), a biodegradable polymer,has excellent optical clarity and high toughness.However,small bubbles are easily generated in the CA solution and hardly eliminated because of the high viscosity and high surface tension of the solution.As is well known, gas bubbles in polymer have an adverse effect on its fracture strength and the breaking elongation.In the presence of gas bubbles, notable different mechanical properties between graphene/cellulose acetate (Gr/CA) composite and pure CA films were found.To further verify that, films were degassed after coating under vacuum condition.