Abstract: The use of conventional curve welding for microstrip antennas can easily lead to insufficient welding strength, and the serious warping of large-area microstrip antennas cannot guarantee welding strength. In order to achieve a reliable mechanical connection of large-area microstrip antennas, a vacuum vapor phase welding model is established based on the multiphase flow VOF equation to predict the temperature field during vacuum vapor phase welding of microstrip antennas. The appropriate welding process window is determined by single factor method. The temperature measurement data shows that the welding simulation error does not exceed 3.5%. The experimental temperature measurement shows that the center of the microstrip antenna is 20℃ higher than the surrounding area, and the porosity of the microstrip antenna and the frame welding is less than 10%. This indicates that the established welding model predicts the temperature field accurately, which can clarify the process parameter threshold for welding experiments. At the same time, applying appropriate torque to the fixture fasteners can effectively suppress the deformation of the microstrip plate and achieve a reliable mechanical connection between large-area microstrip plates and frames.