To investigate the explosion mechanism of molten aluminum-water interactions through computational fluid dynamics (CFD) simulations, a leakage scenario model was developed using the Volume of Fluid (VOF) multi-phase approach to integrate water phase transition with coupled heat and mass transfer dynamics. The simulation successfully reproduced molten aluminum fragmentation during water entry and subsequent vapor explosion, and quantitatively analyzed fragmentation morphology, as well as explosion pressure and temperature distributions. Findings demonstrate that aluminum fragmentation results from the combined effects of hydrodynamic and thermodynamic interactions. Fragmentation significantly enlarges the interfacial contact area between molten aluminum and water, promoting rapid steam generation and subsequent vapor explosion. The detonation process follows a distinct sequential mechanism: "hydraulic dominant deformation-thermal driven fragmentation-steam explosion." Two pressure peaks were observed at the monitoring point, confirming that enhanced heat transfer due to fragmentation is a key factor in steam explosions. The temperature field evolution during molten aluminum-water interaction demonstrated distinct phase-dependent dynamic characteristics. This study systematically simulated the evolution of molten aluminum fragmentation upon contact with water and the subsequent steam explosion, providing fundamental theoretical insights and practical methodologies to improve safety protocols in aluminum production facilities.