• The complete vapor-liquid interface behavior during reflooding is observed. • Discovery and interpretation of the bimodal distribution of droplets. • The three main mechanisms of droplet formation and breakup are discussed. A high-temperature surface reflooding visualization experiment in a single-rod channel was conducted to investigate the transient droplet behavior, which is considered to be critical for heat transfer in Dispersed Flow Film Boiling (DFFB). After the zirconium alloy cladding was heated to the preset temperature, the specimen was subjected to a continuous flow of deionized water under varying input heat flux, coolant subcooling, and apparent reflooding velocity. The temperature history during reflooding was recorded, and the quench behavior was visualized using a high-speed camera. The experimental results show the typical transition mode of inverted annular flow-dispersive flow; at the same time, although the size distribution of droplets conforms to the form of log-normal distribution, the probability of large droplets will increase significantly at higher input heating power. Furthermore, to provide physical support for building droplet distribution models containing more physical mechanisms in the future, several droplet formations and breakup mechanisms, which include the Helmholtz instability, capillary breakage, and rewetting area sputter, have been discussed in this paper.