With the acceleration of the development of energy bases in western China, the transmission distance need to extend to 3000 km and above. The economy of ± 800 kV transmission technology has been seriously challenged. Therefore it is necessary to accelerate the research of longer-distance, larger-capacity transmission technology to promote a wider range of energy resource optimization. The ± 1100 kV UHV DC transmission technology has the advantages of longer economic transmission distance, larger transmission capacity, and lower transmission loss. It can achieve large-scale optimization of energy resources from 3000 to 5000 km, and will play an important role in promoting energy transformation, helping to achieve "dual carbon" goals, and the construction of the Global Energy Interconnection.