Corn starch film, with corn starch as raw material and reinforcing agents and plasticizer added in, was prepared for the carrier of food freshness indicators. The influence of film processing conditions (mixing speed, ultrasonic power and tape-casting technique) on the appearance, mechanical properties and CO2 permeability of the film were studied. Results showed that the mixing speed and ultrasonic power had little influence on the breaking elongation, but over or less mixing speed and ultrasonic power can both bring down the CO2 permeability and tensile strength. The single flow delay film h a d b e tt e r a pp e a r a n c e a n d m ec h a n i c a l p r o p e r ti e s t h a n t h e m u lti f l o w d e l a y , a lt h o u g h t h e m u lt i f l o w d e l a y h a d b e tt e r CO 2 permeability. When the film was made with the mixing speed of 200 r/min, ultrasonic power of 100 W (40 Hz) and single flow delay, it had a good appearance, CO2 permeability and mechanical properties, which can meet the requirement of freshness indicators (CO2 as the characteristic gas).