The present study aims at the development of a numerical simulation program to predict a transient behavior of fiber orientations together with the mold filling simulation for short-fiber-reinforced thermoplastics in arbitrary three-dimensional injection mold cavities. Dinh-Armstrong Model including an additional stress due to the existence of fibers is incorporated into the Hele-Shaw equation to result in a new pressure equation governing the filling process. The mold filling simulation is performed by solving the new pressure equation and energy equation via the finite element/finite difference method as well as evolution equations for the second-order orientation tensor via the fourth-order Runge-Kutta method. The fiber orientation tensor is determined at every layer of each element across the thickness of molded parts with appropriate tensor transformations for arbitrary three-dimensional cavity space.