Abstract: A numerical simulation of two-dimensional isothermal bicomponent coextrusion using the polymer fluid computational package POLYFLOW is presented. Effects of the flow rate ratio of the two kinds of molten polymers and drawing velocity on their flow, the interface shape and extrudate swelling are discussed. Simulation results indicate that, with the increase in volume ratio, ratio of the average wall shear viscosity for the two molten polymers increases. Consequently, difference in the flow properties and layer ratio of the extrudate are increased. With increases in drawing velocity, length of the flat part of the interface increases and profile of the extrudate decreases.