Aiming at the unipolar ground fault problem of offshore wind power grid-connected system via flexible HVDC transmission with the background of special geographic environment of remote islands, a fault-tolerant operation strategy to achieve half rated power transmission during faults is proposed to reduce the loss of outage, and to improve the security and stability of the power grid at the receiving end. Firstly, the transmission topologies of half-bridge modular multilevel converter （MMC） on the island wind power side and hybrid MMC on the onshore grid-connected side are adopted, and their DC line fault characteristics are analyzed; the series-connectable standby transformer networking scheme of the converter station on the wind power side is utilized to avoid wind farms going off-grid due to low-voltage, and to realize the continuous DC voltage reduction operation during the fault period. Further, a wind power side DC energy dissipation device is configured on the island to solve the energy surplus problem of the wind power side converter station under long time load shedding of the wind farm, enable the system to enter a fault-tolerant operation mode with half of its rated power transmission. Finally, based on the PSCAD/EMTDC simulation platform, the effectiveness of the proposed fault-tolerant operation strategy for offshore wind power grid-connected systems with flexible HVDC link under unipolar grounding faults in remote islands is verified.