At present, the construction of offshore wind farms is rapid, and it is developing towards large-scale and far-reaching sea. The demand for power transmission has become one of the hotspots in the research and development of wind power technology. The paper introduces the power transmission methods suitable for offshore wind power: high-voltage AC transmission, high-voltage direct current transmission and fractional frequency transmission , and analyzes its topology, characteristics, research status and results. The application of HVDC transmission technology is extensive, and the technology is diversified according to actual needs. Combining the demand for offshore transmission, we will consider the development situation at the current stage and summarize the power transmission methods of large-scale offshore wind farms.