The accurate measurement of the ground capacitance is helpful to ensure the compensation effect of the arc suppression coil and reduce the damage of the fault to the distribution network. A unified measurement method for ground capacitance and arc suppression coil inductance of resonant grounding system based on signal injection method and fast Fourier transform is proposed. Firstly, the relationship between the neutral voltage and the system parameters is established. Secondly, the nonpower frequency current source is connected to the neutral point, and the current source frequency component of the neutral point is obtained by using the fast Fourier transform to eliminate the power frequency error. Then the unified measurement of ground capacitance and arc suppression coil inductance is realized according to the equivalent circuit. Finally, the simulation model is built by Simulink, which shows that this method is suitable for various types of arc suppression coils. In the threephase asymmetry condition, the maximum errors of ground capacitance and arc suppression coil inductance are 0.11% and 0.1% respectively, and the maximum errors are 1.3% and 1.8% respectively in threephase symmetry condition.