SiO2/MgO/PET composite films with MgO interlayer were prepared by magnetron sputtering machine, and the bonding strength was measured through vertical stretching. The effects of MgO interlayer on the bonding strength of composite films were researched. Results showed that the adhesion force of SiO2/ MgO /PET composite film increased more than 80% compared with SiO2/PET composite film. The process parameters of MgO interlayer played an important role in composite films’ adhesion strength. The adhesion strength increased with the rise of the base pressure, while it firstly increased and then decreased with the rising of sputtering power, argon flow and sputtering time. Among the four process parameters，sputtering time had the greatest effect on bonding strength, followed by radio-frequency power, base pre-ssure and argon flow. The optimal process parameters were obtained as the radio-frequency power of 250 W, sputtering time of 12 min, argon flow of 20 mL/min and base pressure of 0.5×10 -3 Pa.