Abstract: Centralized transmission of large-capacity and long-distance offshore wind power can effectively reduce the development cost. As the main transmission scheme of long-distance offshore wind power, voltage source converter based high voltage direct current (VSC-HVDC) transmission has broad application prospects. This paper comprehensively discusses the key technologies and prospects of VSC-HVDC system for large-capacity offshore wind power. Firstly, the typical AC and DC transmission schemes for offshore wind power are introduced, and the economics of the AC and DC transmission schemes are compared. Then, the key technologies of ±500 kV/2 000 MW offshore wind power transmission system via VSC-HVDC are introduced, and the characteristics of the symmetrical unipolar wiring and the bipolar wiring system are compared from the aspects of overall technical scheme, reliability, and grounding mode. The new problems brought by 66 kV offshore wind farms collection scheme without step-up substation are analyzed. The development directions and challenges of large-capacity offshore wind power transmission technology are pointed out, including DC submarine cables, new transmission modes, intelligent operation and maintenance, control and protection, lightweight of offshore converter platform, etc.