The invention discloses a fault control method and device of an offshore wind power DC sending-out system. A system control strategy under an existing fault only can be used for performing fault control under a certain wind power plant voltage and frequency range, and a DC voltage cannot be enabled to be limited at a value near to the highest limit value. According to the fault control method, a steady-state current expression of a new energy power supply under different control targets is derived with regard to a part of power conversion power supply employing a positive- and negative-sequence dual-synchronous rotation reference frame current controller; on the basis, a power transmission system control strategy is designed due to particularity of offshore new energy equipment; and surplus power on a DC circuit is consumed by low-tunneling suppression resistor, DC voltage rising is prevented, damage of overvoltage to a flexible DC power transmission line is prevented, stable running of the system is maintained, and the running safety and reliability of the offshore wind power DC sending-out system are improved.