Abstract: An experiment system combined with the aluminum industrial production was established to research the effect of different water-aluminum mass ratio for studying on the explosion mechanism of molten aluminum in water. The experimental data indicate that the generation of explosion is closely associated with water-aluminum mass ratio. According to the theory of shock-induced fragmentation producing thermal explosion and the mass and momentum conservation equation, the velocities of different medium or media are variant after shock wave. Aluminum-water relative velocity was investigated to analysis the limitation of explosion by applying water-aluminum mass ratio. The results demonstrate that explosion is prone to occur when the mass ratio ranges from 0.190 to 2.00. The experiment data fit highly for the results, which can determine explosion limitation in the low region of water-aluminum mass ratio.