Recently, short fiber reinforced composites are widely utilized in many structural parts in automobile, infrastructure and electric equipment applications due to their high specific strength, high specific stiffness, long fatigue life and high impact resistance as well as cost effective capability of production. If these parts are exposed to low-velocity impact, significant damages may develop inside the composite parts. These damages may cause reduction of mechanical performances of composite parts. Therefore, predictive analytical or numerical tools are required to evaluate and analyze the integrity of composite parts with impact damages. In this study, a user-defined material subroutine incorporating damage mechanisms of short fiber reinforced composites was developed adopting and modifying various damage models. Then, the subroutine is implemented into ABAQUS to conduct analysis of short fiber reinforced composites parts. The results were compared with those without considering damage mechanism.