Abstract: The mechanism of the re-entrainment phenomenon of the corrugated plate dryer was studied experimentally. The thickness of the falling liquid film on corrugated plate was measured by means of the planar laser induced fluorescence method on a visualization test bench, and then, an empirical relationship between liquid film thickness and liquid film Reynolds number was proposed. On this basis, the liquid film critical breakup conditions were studied. The results show that the liquid film thickness at the cross section is nonuniform, and the maximum thickness point of the cross-section gradually moves from edge area to the central area as the flow rate of the liquid film increases. Furthermore, the average thickness of liquid film increases as liquid film falls down. The critical velocity resulting in liquid film breakup decreases when liquid film thickness increases.