Abstract: In the process of the interaction between the melt and the coolant (FCI), the hydrodynamic fragmentation of the molten droplet has an important influence on whether the steam explosion will happen or not and how intense it will be thereafter. The traditional numerical study of molten droplet hydrodynamic fragmentation usually only considers the direct contact of the melt with the coolant, which is a two-phase system, without considering the existence of vapor film. However, the core melting temperature is above 2500 K and vapor film can be rapidly generated around the melt, thus, the characteristics of heat transfer and flow resistance will be changed. In this paper, the numerical study was carried out on the molten droplet hydrodynamic fragmentation process with the presence of a vapor film using a three-phase system based on the PLIC-VOF （piecewise linear interface construction-volume of fluid） interface tracking method. Through analyzing the interfacial properties of the molten droplet in the process of fragmentation, it is found that the molten droplet fragmentations are more severe with the increase of Weber number and the vapor film has a negative effect on the hydrodynamic fragmentation.