The present study has been focused on the implementation of three treatments with different steps in order to reduce the content of impurities, hemicellulose, lignin and silica. The crystallinity, morphology and thermostability of the rice husk after the treatments have been investigated by using X-ray diffraction, scanning electron microscopy and thermogravimetric analysis. Then, PLA bio-composites with different filler contents have been prepared using a twin extruder. The thermal and mechanical properties of the resulting biocomposites have been investigated and correlated with the observed morphologies and thermostability. The mechanical and thermostability properties turned out to be strongly improved the more the non-cellulosic components diminish. These data have been compared with those of analogous compounds containing different natural fibers. Finally, this work has also demonstrated that an agro-industrial waste as rice husk can be recycled for improving PLA properties.