Abstract: The development of miniaturization, intelligence and high integration of electronic components urgently requires packaging materials with efficient thermal management and thermal conductivity performance. In order to improve the mechanical and thermal conductivity of thermoplastic polyurethane (TPU), Al₂O₃/MWCNTs/TPU nanocomposites were prepared using TPU as matrix and Al₂O₃ and MWCNTs as nano-fillers based on multi-scale structure and interface design. The microstructure, mechanical properties, heat resistance performance and thermal conductivity of the synthesized filler and TPU composites were investigated. FTIR proved that hydroxylation modification of Al₂O₃, amination modification, acidification of MWCNTs, and amide bonding of Al₂O₃/MWCNTs was successful. The results of POM and FESEM analysis show that the dispersion of the modified fillers in the matrix is relatively uniform, and the interaction between Al₂O₃-MWCNTs could be seen in the ternary nanocomposites. The best mechanical properties of Al₂O₃/TPU nanocomposites were obtained at 5% filler content, and the best values of MWCNTs/TPU and Al₂O₃/MWCNTs/TPU nanocomposites were obtained at 0.5% filler content. Moreover, the mechanical properties of ternary nanocomposites were significantly improved compared with binary nanocomposites. TGA analysis results show that the thermal stability of the nanocomposites is greatly improved compared with that of pure TPU. Thermal conductivity analysis results show that the thermal conductivity of nano-composites increased by 19.1% after the addition of modified Al₂O₃ and 95.1% after the addition of modified MWCNTs, while the thermal conductivity of ternary nano-composites increases by 124.6% compared with pure TPU under the same filler content.