Abstract: The nanometer calcium carbonate (Nano-CaCO₃)/polylactic acid (PLA) composites was melt-compounded by twin-screw exturder with Nano-CaCO₃ and PLA as raw materials,maleic anhydride grafted ethylene-octene copolymer (POE-g-MA) as compatibilizer.SEM,DSC,TG,capillary rheometer (CR) and universal testing machine were used to perform the interfacial compatibility,thermal properties,rheological properties and mechanical properties of Nano-CaCO₃/PLA matrix composites,respectively.The results show that the aggregation phenomenon in the PLA matrix increases compared with pure PLA when the content of Nano-CaCO₃ increases to 15wt%.The crystallinity,the maximum thermal decomposition temperature and the tensile strength of Nano-CaCO₃/PLA composites decrease by 1.9%,15.5℃ and 28.2%,the flexural strength and elongation at break increase by 37.5% and 29.3%,respectively.And the interfacial compatibility of Nano-CaCO₃/PLA composites with 4wt% POE-g-MA improves,the crystallinity and the tensile strength of sample decrease by 4.2% and 25.2%,the maximum thermal decomposition temperature,the flexural strength and elongation at break of sample increase by 5.8℃,25.3% and 174.4%,respectively.The shear viscosity of Nano-CaCO₃/PLA composites increases due to thaddition of POE-g-MA.