Abstract: This paper presents a comprehensive analysis of the transport processes of propellant in tank of spacecraft in different gravity. The motion of the liquid-vapor interface of propellant in the tank of on-orbit spacecraft is investigated numerically by solving the incompressible Navier-Stokes equations using the VOF method coupled with the surface tension effect under micro-gravity environment. The objectives of this study are to examine the robust method of controlling the interface transformation of the two phase flow by comparing and analyzing the effects of gravity and contact angle as the typical parameters. Results show that, the gravity effect plays a dominant role in determining the shape of gas-liquid interface and the relative location of the gas-liquid phase in the tank at large Bond number; when the Bond number is small enough, the wettability effect exert a great influence.