In order to make clear the effect of liquid entrainment on the distillation tray efficiency, a new type of mixing pool model is developed in this paper to calculate the apparent distillation tray efficiencies when the liquid entrainment happens for the counter current tray with vapour unmixing between trays and liquid partially mixing on trays. The analytical solutions are obtained and compared with the calculated results of Bennett's experimental correlations. The mean relative error between them is 5.6% for the range of 0 less than or equal to Pe less than or equal to 1000, 0.5 less than or equal to lambda less than or equal to 3.0 and 0.4 less than or equal to E less than or equal to 1.0. The result shows that the model presented in this paper is reliable.