A method for determining a parameter of a passive impedance adapter applicable to VSC-HVDC, wherein, the passive impedance adapter comprises a main capacitor, a main resistor and a branching inductor; the main capacitor is connected in series with the main resistor; the branching inductor is connected in parallel across the main resistor; the method for determining the parameter comprises steps of: S1. obtaining a VSC-HVDC impedance, and obtaining a VSC-HVDC impedance curve X(/) based on the VSC-HVDC impedance; S2. estimating an upper limit value of the main capacitor in the passive impedance adapter; S3.calculating an adapter parameter curve X adapter ( f) associated with the main capacitor, the branching inductor and the main resistor of the passive impedance adapter; S4. determining a value of the main capacitor within a range of the value of the main capacitor, and varying a value of the main resistor until min[X( f)- X adapter ( f)] is maximized; determining whether min[X( f)- X adapter ( f)]> k holds at that time; wherein, k is a preset threshold; S5. if min[X( f)- X adapter ( f)]> k does not hold, increasing the value of the main capacitor and performing steps S2-S4 until min[X( f)- X adapter ( f)]> k holds when the value of the main capacitor is less than the upper limit value of the main capacitor, outputting and storing current values of the main capacitor, the branching inductor and the main resistor as available parameters in an available parameter set; if min[X( f)- X adapter ( f)]> k does not hold when the value of the main capacitor is a maximum value within the range of the value of the main capacitor, performing step S4 with a value of k being reduced; S6. if min[X( f)- X adapter ( f)]> k holds, reducing a value of the main capacitor C until min[X( f)-X adapter ( f)]> k does not hold, and outputting and storing the values of the main capacitor, the branching inductor, and the main resistor during the reducing of the value of the main capacitor C as available parameter in the available parameter set; S7. selecting the available parameter from the available parameter set. S1. obtaining a VSC-HVDC impedance, and obtaining a VSC-HVDC impedance curve X(/) based on the VSC-HVDC impedance; S2. estimating an upper limit value of the main capacitor in the passive impedance adapter; S3.calculating an adapter parameter curve X adapter ( f) associated with the main capacitor, the branching inductor and the main resistor of the passive impedance adapter; S4. determining a value of the main capacitor within a range of the value of the main capacitor, and varying a value of the main resistor until min[X( f)- X adapter ( f)] is maximized; determining whether min[X( f)- X adapter ( f)]> k holds at that time; wherein, k is a preset threshold; S5. if min[X( f)- X adapter ( f)]> k does not hold, increasing the value of the main capacitor and performing steps S2-S4 until min[X( f)- X adapter ( f)]> k holds when the value of the main capacitor is less than the upper limit value of the main capacitor, outputting and storing current values of the main capacitor, the branching inductor and the main resistor as available parameters in an available parameter set; if min[X( f)- X adapter ( f)]> k does not hold when the value of the main capacitor is a maximum value within the range of the value of the main capacitor, performing step S4 with a value of k being reduced; S6. if min[X( f)- X adapter ( f)]> k holds, reducing a value of the main capacitor C until min[X( f)-X adapter ( f)]> k does not hold, and outputting and storing the values of the main capacitor, the branching inductor, and the main resistor during the reducing of the value of the main capacitor C as available parameter in the available parameter set; S7. selecting the available parameter from the available parameter set.