The invention discloses a configuration method for secondary frequency modulation reserve capacity of a direct current islanded sending power grid, comprising: quitting the FLC function of the direct current islanded sending power grid; under the condition of maximum power shortage delta P1 resulted from the N-1 fault of the sending power grid, calculating primary frequency modulation reserve capacity P1-1 needed to be reserved for recovering the power grid frequency to a primary frequency modulation control objective F1; under the condition of power shortage delta P1, calculating the secondary frequency modulation reserve capacity P1-2 needed to be reserved on the basis of the P1-1 for recovering the power grid frequency to a secondary frequency modulation control objective F2; under the condition of maximum power shortage delta P2 resulted from the N-2 fault of the sending power grid, calculating primary frequency modulation reserve capacity P2-1 needed to be reserved for recovering the power grid frequency to the F1; under the condition of power shortage delta P2, calculating second frequency modulation reserve capacity P2-2 of the system on the basis of the P2-1 needed to be reserved for recovering the power grid frequency to the F2; injecting the FLC function; under the condition of power shortage delta P2, calculating secondary frequency modulation reserve capacity P3-2 needed to be reserved for recovering the power grid frequency to the F2 and recovering the FLC direct current power modulation quantity to 0 before the secondary frequency modulation action.