The effects of the geometrical shape of extrusion dies and the fiber orientation at the entrance on fiber orientation and die swell were analyzed numerically by finite element method. The fiber orientation and the interaction among the fibers were analyzed by way of the orientation tensors. The fibers near the die wall aligned along the flow direction regardless of its initial orientation. But the fibers near the center line retained its initial orientation. It was verified that the use of extrusion dies of contraction or expansion entrance made it possible to control the fiber orientation significantly. The C_I value which represents the interaction among fibers also affects the orientation and the die swell. The orientation disturbed and the swell ratio increased as the C_I increases. The swell ratio decreased in expansion die but increased in contraction die as the L/D ratio increases. The swell ratio when fibers were introducted as aligned state was smaller than the case of randomly introduced state.