Analytical solutions for flow behavior in the coextrusion of a core polymer melt encapsulated by a sufficiently low viscous skin polymer melt were developed for rectangular arid converging channel geometries. The results indicated that when the skin shear viscosity was hundred times lower than that of the core essentially all the shearing gradient was pushed in the skin hence the core polymer was located in a pure elongational flow region. This paper also discussed the effect of flow rate ratio and viscosity ratio on the velocity profile, pressure gradient and interface position of the coextrusion. Physical data for polyethylene as a skin material and polypropylene as a core material was used in this study.