The invention provides a method and a system for reactive power replacement of a phase modifier of a direct current receiving end area. The method comprises the following steps of computing a currentdynamic reactive power margin of a phase modifier node and a reactive power output relative value of the phase modifier according to information of an alternating-current and direct-current hybrid power grid; if the dynamic reactive power margin of the phase modifier node at the current moment is smaller than a margin threshold value or the reactive power output relative value of the phase modifier is larger than an output threshold value, obtaining a reactive power output predicted value of non-phase-modulation reactive power compensation equipment according to the information of the power grid; and at the moment corresponding to the reactive power output predicted value, increasing the reactive power output of the non-phase-modulation reactive power compensation equipment to the reactivepower output predicted value, and correspondingly reducing the reactive power output of the phase modifier. According to the method and the system, a condition of the dynamic reactive power margin ofthe phase modifier node is quantitatively evaluated, and when the dynamic reactive power margin is insufficient, reactive power resources of the phase modifier are released through the reactive powerreplacement, so that more damage to the system, which is caused by cascading faults due to the fact that the dynamic reactive power storage is insufficient when the next fault occurs, can be avoided,and the safety and the economy of operation of the power grid are improved.