Abstract: Numerical study on the process of water droplet impinging initially on water film deposited on wire mesh surface in wire mesh demister was carried out through the VOF multiphase flow model to predict the mechanism of reentrainment caused by big droplets under rather high steam velocity. In this paper, an intensive numerical simulation to study and evaluate the influencing factors of droplets, such as droplet size, initial velocity and water film thickness on re-entrainment phenomenon, was presented to support the design of wire mesh demister. Numerical results show that water droplet size and impacting velocity are the two main factors to influence the occurrence of splash, and the resulting secondary small droplets are the important proportion of the re-entrainment in a wire mesh demister of freshwater generator. Whether or not splash occurs when a big droplet impinging onto the wire mesh depends on the threshold K_cr＝Oh•Re^a. And when the value of K is greater than K_cr, the re-entrainment will appear definitely.