Abstract: Taking the ultra-thin vapor chamber for heat dissipation of the proton exchange membrane fuel cell stack as the research object, a three-dimensional steady-state numerical model was constructed by using the porous medium heat transfer model, laminar flow model and Brinkman equation, and the phase change mass transfer at the gas-liquid interface was determined by mass conservation.Steady-state characteristics of the ultra-thin vapor chamber under the normal working conditions of saturated with liquid wick were studied. The results show that the ultra-thin structure and the presence of the support column make the internal pressure drop larger.With the increase of convective heat transfer coefficient in the condensing section, the temperature difference increases first and then decreases, and the internal pressure drop also increases significantly. With the increase of heat flux density, the temperature uniformity first increases and then decreases, and the thermal resistance continues to decrease. The change of porosity has little effect on the equilibrium final state. The increase in permeability will greatly reduce the liquid pressure drop in the wick, which is beneficial to phase change circulation.