Abstract: On the basis of the research on vibration mode of floating droplets，this paper discusses Leidenfrost

effect and the threshold radius of Leidenfrost stars in various stages. It is found that the vibration modes of floating

droplets correspond to radius range. Both the theoretical and experimental results indicate that floating droplets are

divided into three main modes by two thresholds. When the radius is smaller than the lower boundary of threshold，

droplets are contracted to a spheroidal one because of surface tension; on condition that the radius is larger than the

outer boundary of threshold， the pressure difference between the inner and external part of droplets is negative，

which destroys the original vibration of droplets and forms a bubble at the bottom of droplets. In this case that floating

droplets between two modes， forms Leidenfrost stars and the modes of stars is linearly enlarged with the increase

of radius. In contrast， the modes of stars decrease with evaporating.

Key words: Leidenfrost effect, threshold radius, presentation modes