In Algeria, considerable quantities of olive husk are rejected as waste causing consequently inconvenience to environment. Therefore, our work is focused on the valorization of this waste by its incorporation in PLA matrix to obtain biocomposite materials with specific performances. The hydrophilic nature of natural fibers affects negatively its adhesion to hydrophobic polymeric matrix. To improve interfacial adhesion, chemical treatment of the fiber can stop the moisture absorption process clean the fiber surface, chemically modify the surface or increase surface roughness. Therefore, our paper reports the effects of three chemical surface modifications (alkali, silane and benzoylation) on the properties of biocomposites based on poly lactic acid (PLA) reinforced with olive husk flour (OHF) incorporated at 10, 20 and 30 wt.%. From the samples produced by extrusion-injection, the thermal and mechanical properties of biocomposites with both treated and untreated olive husk flour are reported and compared with the properties of the neat matrix. The results show that the mechanical and the thermal properties of the biocomposites with treated fiber are better than that of neat PLA and the biocomposites with untreated fiber.