Abstract: To clarify the operational characteristics and propellant management liquid retention stability of plate-type tanks during in-orbit operation, this paper presents a numerical investigation of the liquid retention stability of a plate-type propellant management system. A three-dimensional numerical model of a plate-type methane propellant tank is developed based on the volume of fluid method coupled with the continuous surface force model for surface tension. The effects of different contact angles and residual gravity on the evolution of the gas–liquid interface and the variation of the liquid center of mass are systematically analyzed. The results indicate that decreasing the contact angle enhances the liquid collection capability of the device and increases the liquid retention margin. Within the residual gravity range of 0～5×10⁻³ g, the liquid remains stably accumulated in the vicinity of the vane corners and the central column, demonstrating strong resistance to residual gravity. The present study provides a useful reference for the application and structural design of plate-type propellant management devices in methane propellant tanks.