The extrudate swell of semiconcentrated fiber suspensions was investigated numerically by using a constitutive equation based on the continuum theory, which takes the interaction effect between flow and fiber orientation into account. And the orientation equation expressed in terms of the orientation tensor was solved simultaneously to obtain the fiber orientation distribution, in which the interaction effect among fibers was taken into account by adding a phenomenological diffusion term. In the simulations of the axisymmetric extrudate swell of fiber suspensions, the die swell ratio decreased as the suspension intensity increased when the fibers at the die inlet were aligned. But in the case of random orientation states of fibers at the die inlet, roughly thought as the case of short dies, the swell ratio increased, however. Different trends in the swell ratio caused by the different fiber orientation states at the die inlet could be explained in terms of the elongational viscosity difference between the outer surface part and the inner core part.