The heat sealing process of Al/PE film mechanism based on diffusion theory is investigated in this paper. Parallel horizontal sealing mechanism is designed and heat sealing strength test is conducted. Considering the sealing performance of Al/PE film as the objective function, establish ternary quadratic mathematical sealing strength model about the heat sealing temperature, dwell time and film thickness three factors. Through analyzing the impact of heat sealing process parameters on sealing performance, the optimization heat sealing process parameters are determined. All the work provides a practical guidance and theoretical basis for heat sealing packaging machine design and parameters determination.