Long fiber reinforced thermoplastics, with reducing costs and vehicle weight, continue growth in automotive. Their mechanical properties including strength, stiffness, and impact are strongly influenced by a length distribution of breakage fiber. Recently, the Phelps-Tucker fiber attribution model was proposed to predict the length distribution. In this work, a set of measurement data of fiber length in shear-induced screw processing has been used to validate the fiber attribution model and then determine model-parameter value. Furthermore, it is significant to present the length pattern of breakage fiber during mold filling via three-dimensional injection molding simulations, as compared with related experimental data.