Abstract: In order to prepare the polylactic acid (PLA) composites with excellent strength and toughness, octa (propylglycidyl ether) polyhedral oligomeric silsesquioxane (Ope-POSS) nano particles were added into PLA, and PLA grafted by glycidyl methacrylate (PLA-g-GMA) was added as compatibilization and toughening component firstly. Then, PLA-g-GMA/Ope-POSS/PLA composites were prepared by melt blending method. Finally, by the characterization of morphological structure, thermal properties, mechanical properties and hydrophobicity of the composites, the effects of the addition of Ope-POSS nano particles and PLA-g-GMA on the properties of the PLA composites were analyzed. The results show that the addition of PLA-g-GMA plays an effective compatibilizing effect for Ope-POSS nano particles, resulting in the better dispersion of Ope-POSS nano particles in the composites. With the amount of well dispersed Ope-POSS nano particles increasing, the strength, thermostability and hydrophobicity of PLA composites are all improved significantly, and the toughness is also advanced with PLA-g-GMA content increasing. When the PLA-g-GMA and Ope-POSS nano particle contents are 4wt% and 3wt% of PLA respectively, the properties of PLA-g-GMA/Ope-POSS/PLA composite are optimal. The obtained conclusions provide theoretical guidance for the further investigation of POSS hybridized PLA composites.