Microinjection molding is one of the methods used to fabricate micro scale plastic components. Addition of reinforcement in the thermoplastic materials can enhance the mechanical properties of the molded components. Due to the small dimension in micro features, the filling of reinforcements into those features is more difficult than into the main body of the component. This study is to investigate the filling efficiency in micro features for different reinforcements. The filling efficiency in the micro feature is almost the same as that in the main body of the component for using the reinforcement in nano size. For milled glass fibers, which have a distribution of the particle size, higher fiber content has better filling efficiency in the micro features. On the other hand, the filling efficiency is not affected by the volume fraction for using short glass fibers.