The invention discloses a power out-of-limit quick control method and system of an island convertor station connected with a passive power grid. The power out-of-limit quick control method comprises the steps of performing real-time monitoring on the active power of a controlled fracture surface on the primary side of two converter transformers of the controlled fracture surface to obtain a real-time active power value; transmitting the real-time active power value to an island convertor station power out-of-limit quick control centre, wherein the island convertor station power out-of-limit quick control centre judges whether the real-time active power value reaches a preset control red line threshold value or not; and when the real-time active power value reaches the preset control red line threshold value, enabling a new energy control master station to transmit a power adjustment instruction to an execution station according to the regulation and control sequence to allocate, and realizing decreasing of the active power through the execution station. By virtue of the control method, the active power of the island convertor station can be limited, and the control method can be applied to all systems transmitted by a flexible direct current power grid and is large in coverage range; and compared with transformation of a wind power plant or a convertor station, the control system has the advantages of convenience in realization, low investment and the like.