Abstract: With the rapid development of aerospace technology, the heat dissipation requirements of high-power consumption and large size electronic components need to be solved urgently. The large-area thin-walled vapor chamber based on the passive two-phase heat transport mechanism provides a promising choice for efficient heat dissipation. At the same time, the structural characteristics of large-area and thin-walled cavity also bring a series of challenges to its flow heat force coupling design.Therefore, based on Finite Element Analysis (FEA) and the theory of elasticity, this study elucidates the mechanical constitutive relationship of each structural parameter of the load-bearing unit, and reveals the changing law of the cavity stress under the pressure field, temperature field, and thermo-mechanical coupling field: The maximum stress in the bearing unit is exponentially related to the porosity and the bearing column diameter. When only the internal temperature field of the cavity is considered, the thermal stress in the cavity is positively related to the bearing column diameter and negatively related to the porosity and the thickness of the vapor chamber. The temperature and pressure fields have different tensile and compressive stress effects on different parts of the loading structure, and the apparent maximum stress in the cavity is actually the result of the two stresses superimposing or cancelling each other.