Abstract: High-temperature alkali metal wick heat pipe is mainly used in special applications, such as nuclear engineering and aerospace. Alkali metal working mediums differ in thermophysical properties from low-temperature working mediums. The internal mechanism of a wick heat pipe is essential, which couples flow heat transfer and capillarity, thus deserving to study. In this paper, the capillary evaporation thin film model of the wick was established based on the precursor film theory and the evaporation meniscus theory. Considering the electronic component of disjointing pressure and heat conduction effect on liquid sodium film, capillarity characteristics on wick surface were analyzed, and the influence of different operation parameters was explored, including the thermodynamic parameters and geometry parameters. The thermodynamic parameters include the operating temperature, overheat, evaporation coefficient and condensation coefficient. The geometry parameters include the size of the pore and wire and the location of the liquid film contact area. Simulations show that phase change of liquid sodium mainly occurs in the intrinsic meniscus. Besides, operating temperature, overheat, evaporation coefficient and condensation coefficient affect capillarity characteristics by changing the thermophysical properties of the working medium. These thermodynamic parameters have a slight effect on the apparent contact angle but have a significant effect on the heat flux rate. The dynamic adjustment ability of the wick is related to the wire diameter and pore size. The evaporation area and length of the three-phase contact line, which depend on film contact position and operation temperature, affect the mechanical equilibrium, heat, and mass transfer capacity of the wick, and change capillary pressure provided by the film on screen wick surface. In the process of liquid film retreat into the wick, when the contact angle is constant, the capillary force increases at first and then decreases. It reveals that the liquid film has dynamic adjustment ability, and can automatically adapt to the required evaporation and pressure balance with the change of the heat load for a certain range. Nevertheless, the condition of high operating temperature may cause the mismatch between the capillary head and the pressure loss, leading to dry out in the wick. This work may provide a reference for the applications of alkali-metal wick heat pipes.