The aim of this work was to study the effects of ultra high pressure on the structure and properties of the film, as well as the interaction between the film and the food simulant under high pressure processing. LDPE packaging bags were selected as the study object, and the 10% and 95% ethanol were chosen as food simulants in the LDPE packages. In a ultra high pressure device, pressure of 200, 300, 400 MPa was applied respectively for 5 and 15 min, and the medium temperature was 20 and 60℃ , the changes in the structure and properties of the film as well as the total amount of nonvolatile food simulant after storing under these conditions for 7, 14 and 21 days were determined. The increase of pressure and temperature could enhance the segment motion, leading to increased degree of crystallinity of LDPE film. Meanwhile, the tensile strength was also enhanced, but the change was not significant. With the increasing pressure, the oxygen transmission rate decreased. For LDPE package containing 95% ethanol solution, the oxygen transmission rate was lower than that containing 95% ethanol solution. The concentration of food simulant also significantly affected the total amount of nonvolatile matter. The higher the concentration, the lower the total amount of nonvolatile matter and the smaller the migration. Pressure, temperature and content of food simulant all influenced the interaction between LDPE and ethanol .