The invention provides an AC/DC coordination control method and system. The AC/DC coordination control method comprises the following steps of adjusting an active control mode of a flexible DC converter station when AC power grid island occurs in a flexible DC sending end; calculating power surplus after running of the power grid island; and performing AC/DC coordination control according to the power surplus. The AC/DC coordination control method provided by the technical scheme is used for providing reference for aspects such as planning and running of a power grid accessed to flexible DC engineering, and a basis is provided for design of a safe and stable control system of the island passing through the flexible DC sending system.