With a series problems such as global energy and resource shortage, several countries have begun to increase investment for new energy development. Because wind energy is renewable, clean and pollution-free, it is widely used in the entire world. Offshore wind farm does not take up valuable land resources, and the sea has abundant wind energy resources so that the wind turbine can achieve greater unit capacity. Therefore, the development of offshore wind farm has become a new direction of China's Green Energy Development. In this context, the study of large-scale offshore wind farm and the impact on the power system is necessary. Based on the analysis of Shanghai Nanhui wind farm's operation, this paper discusses the interconnection of the Donghai Bridge offshore wind farm and the short-circuit capacity, power quality, as well as the reactive power.