Abstract: The cryogenic liquid krypton tank will be in microgravity environment for more than several hundred seconds during MECO(Main Engine Cut-off)phase, its internal heat transfer and phase change have an important impact on the performance of the storage and supply system of the large orbit transfer vehicle. Establishing a CFD model of liquid krypton tank, the effects of gravity level, initial liquid krypton temperature and initial filling rate on the thermal stratification and pressure variation of liquid krypton tank in microgravity were studied by using VOF method and Lee gas-liquid phase change theory. The results show that, in the microgravity conditions, the tank pressure rise rate are lower than in the ground condition, the pressure rise rate of tank in g₀ is 1.843 times, 1.98 times and 2.04 times of 10^-4g₀, 10^-5g₀ and 10^-6g₀ respectively, the degree of temperature stratification (2-3 K) is much lower than that of ground conditions (90 K). Under different initial liquid krypton temperatures, the tank pressure decreases first and then increases with time, and the lower the initial liquid krypton temperature is, the smaller the pressure rise rate of the tank is. There is a critical initial fill ratio of the tank in microgravity, when the initial fill ratio is > 70%, the pressure rise rate increases with the increase of the initial fill ratio, and when the < 70%, the pressure rise rate of the tank decreases with the increase of the initial fill ratio.