The liquid phase mass transfer resistance in the Rotational-current tray is one of the most important factors in its design and performance. In this report, the holding time of liquid on the tray was studied experimentally by water-air system, and then the desorption tests were carried out by water-oxygen-air system that the liquid phase resistance were controlling. From the results of these experiments, it was found that the gas flow rate and the holding time of liquid on the tray control the tray efficiency strongly. Thus, the experimental equation for the number of transfer units based on liquid phase was derived. And also, it was found that this type of tray can be operated at high efficiency with a higher gas rate than the Kittel tray and the sieve tray without downcomer.