Abstract: In order to obtain excellent properties of poly (lactic acid) based biodegradable composite, organic modified montmorillonite (OMMT) with dimethyl dioctadecyl ammonium chloride was used as a non-reactive compatibilizer. The organic modified montmorillonite/poly(lactic acid)-poly(butylene succinate) (OMMT/PLA-PBS) composites were prepared by direct melt blending method. The effect of OMMT contents on compatibility between PLA and PBS, and mechanical properties of the composites were investigated in this work. Morphological analyses reveal that OMMT can significantly reduce the particle size and result in uniform distribution of the dispersed phase PBS. The OMMT distributes in the interface between PLA and PBS can act as compatibilizer similar to block copolymer and increases interface adhesion between PLA and PBS. The dynamic rheological results indicate that OMMT forms a three-dimensional network structure at 3wt% OMMT. From dynamic thermo-mechanical analysis, glass transition temperatures of PLA and PBS in the composites get closer with the addition of OMMT. At 1wt%, the degree of glass transition temperature convergence is maximum, corresponding to the best compatibilization. Thermal data show that the crystallinity of PLA in composites first increases and then decreases by addition of OMMT. The crystallinity of PLA reaches maximum of 12.7% at 1wt%. The results of mechanical properties show that the comprehensive mechanical properties of OMMT/PLA-PBS composites reach the best when the OMMT content is 1wt%. The tensile strength and impact strength are 62.5 MPa and 12.6 kJ/m², respectively, which are 32.1% and 80% higher than those of the PLA-PBS blend.