The liquid flow on a single-pass sieve distillation tray is simulated with a three-dimensional computational fluid dynamics (CFD) program with the K-epsilon turbulence model. In the model, a source term S-Mi is formulated in the Navier-Stokes equations to represent the interfacial momentum transfer and another term SC is added to the mass transfer equation as the source of interfacial mass transfer. The simulation provides the detailed information of the three-dimensional distribution of liquid velocity on the tray, the circulation area and the concentration profile along the height of liquid layer.