This paper analyzed the localization status of key components and systems in offshore wind turbines such as blades, spindles, electrical systems, and control systems.In view of the localization weaknesses existing in the components and systems of offshore wind turbines, the localization of blades, main bearings, converters and programmable logic controller (PLC) was carried out by using the ideas of theoretical analysis, material/component selection, component development, test verification and overall assembly, and 5 MW offshore wind turbines were assembled with the developed localization components and systems. The localization rate of the unit was more than 95%. The results show that most of the components and systems of offshore wind turbines have the conditions for localization, but some technologies, such as blade design, still rely on imports, and a few core components are still missing in China.