Abstract: Fluid sloshing behavior in cryogenic propellant tanks under variable acceleration conditions leads to severe gas-liquid mixing, posing a significant threat to the safety and stability of spacecraft. This paper focuses on the dynamic behavior of propellants during the return phase involving attitude adjustments of a reusable launch vehicle. Through numerical simulations, the effects of different tank structures and varying acceleration conditions on fluid dynamics are systematically evaluated. A three-dimensional scaled numerical model based on the Volume of Fluid （VOF） method was established to analyze the gas-liquid interface behavior, liquid oxygen outflow through transverse perforated plate, and changes of centroid under different tank structures, negative gravity, and lateral acceleration conditions. The results demonstrate that the transverse perforated plate effectively restrains liquid oxygen outflow, while the vertical cruciform perforated plate significantly suppresses lateral sloshing. In quantitative terms, the anti-sloshing index for the tank equipped solely with a transverse plate was measured at 45.3%. In contrast, the composite configuration, which integrates both transverse and vertical cruciform plates, achieved a notably higher anti-sloshing index of 60.2%. It was also observed that increased negative gravity correlates with greater liquid oxygen outflow, more pronounced sloshing amplitudes, and altered bubble formation and dynamics. Similarly, higher lateral accelerations result in an increased pressure differential across the transverse perforated plate, which in turn amplifies sloshing intensity and outflow rate.The composite perforated plate design shows a substantial improvement in the anti-sloshing index, effectively mitigating liquid oxygen outflow and sloshing under complex motion conditions. These findings provide valuable insights for the optimized design of propellant tanks in reusable spacecraft, highlighting the importance of integrated baffle arrangements. Moreover, the study underscores the critical influence of acceleration intensity on fluid dynamic behavior, suggesting that mission planning and vehicle design must adequately account for variable overload conditions to ensure system safety and performance.