Abstract: The two-dimensional entrainment distribution at different heights in a 1.2m diameter sieve tray was studied experimentally by the capture weighing method for the air-water system under various operating conditions. The entrainment was not uniformly distributed. On the basis of a great number of experimental data, orthogonal polynomial regression was used to find a two-dimensional non-uniform entrainment distribution function. Numerical solution was developed for estimating tray efficiency with entrainment by using the two-dimensionnl fixed number mixing pool model. The effect of entrainment distribution on plate efficiency was also discussed.