Abstract: In order to understand the complicated fuel-coolant interaction and steam explosion during severe accident of nuclear reastors, the fragmentation process of high temperature molten metal drop interacted with water is investigated by experiment. The influences of initial temperature of melt drop, the temperature of water, the release distance of melt drop and the property of the materials are analyzed by comparing the appearance of the debris generated during interaction. The fragmentation process of melt drop is observed by high-speed camera. The results show that the initial temperature of melt drop, the temperature of water and the property of the materials are sensitive parameters for the fragmentation, but the release distance of melt drop is not an important parameter under the conditions of this experiment.