Abstract: DC collection and transmission is one of the main developing directions of large-scale offshore wind power system. In order to achieve low-cost, high efficiency and high reliability all-DC offshore wind power collection and transmission, this paper proposed an all-DC offshore wind power networking scheme based on multi-functional DC collector. By introducing the DC collector concept to realize energy collection and cascade boost, the proposed networking system not only greatly reduced the wind turbine converters scale and offshore converter platform, but also eliminated the influence of power fluctuation captured by wind turbine on the series voltage of internal grid in the wind farm, so that each wind turbine achieved the maximum power point tracking operation and maintained the original control and protection architecture. In addition, the introduction of DC collector made the operation of offshore wind power system more flexible, and various operating modes were considered such as fault isolation, dynamic cut-in/out, and DC energy consumption operation etc., which provided a practical solution for the construction of long-distance and large-capacity offshore wind farms. Finally, the effectiveness of proposed scheme was verified by simulation model of 400MW all-DC offshore wind power system.