With the development of modern power systems, especially that of the global energy internet, high-voltage, direct current (HVDC) cable power transmission will play an important role in the future. The key problem of HVDC cable power transmission is the need for novel cable insulation materials that have high performance, recyclability, and higher working temperature to replace traditional crosslinked polyethylene. This paper investigates the thermal and electrical properties of polypropylene (PP)/Al2O3 nanocomposites as a potential recyclable HVDC cable insulation material. The developed nanocomposites exhibit excellent thermal and electrical properties with the introduction of Al2O3 nanoparticles. Particularly, the space charge accumulation is greatly suppressed. Keywords: Global Energy Internet, Power transmission, HVDC cables, Eco-friendly insulation material