PET/PE composite film is widely used in food and drug packaging, but there is heat sealing quality unstable problem in the production process. Influencing factors of heat sealing quality of PET/PE composite film were studied through heat sealing and tensile test. The influences of heat sealing direction, heat sealing temperature, and heat sealing speed on heat sealing quality were compared and analyzed. The optimal heat-seal processing parameters of PET/PE composite film were summarized.