The work aims to solve the problem of larger temperature difference of the hot cutter’s heat sealing surface in the heat sealing device for bag making machine. The parametric modeling of heat sealing device for bag making machine was established by Solidworks software. The steady state temperature was simulated by calling Ansys Workbench plug-in to analyze the distribution of its temperature field. Then, the internal structure of the electric heating plate was designed by increasing the number of the electric heating pipes. Finite element analysis of the improved model and the length optimization design of the mounting hole of electric heating pipe in the electric heating plate were carried out. Finally, the experimental verification thereof was conducted. The experimental results showed that the simulation results were in good agreement with the measured data. The optimization and improvement design of the temperature field simulated based on the finite element analysis could have the temperature difference of heat sealing surface of the heat sealing device reduced from 4.4 ℃ to 2.9 ℃. The improved design of the internal structure of electric heating plate simulated based on the temperature field can obtain satisfactory temperature difference effects of the heat sealing surface.