A new method is proposed to measure the capacitive and impedance current of resonance grounding power networks based on the increments while stabilizing the phase of the zero-sequence voltage. For the arc suppression coil and damping resistance in parallel grounded power networks, the grid-to-earth capacitance and resistance can be calculated accurately through switching the parallel damping resistor while stabilizing the phase of the zero-sequence voltage twice. The simulation model is established and experiments are carried out in MATLAB to verify the correctness of this tuning method. This tuning method is simple, measured with less data needed, and can be used in not only the follow-resonant arc-suppression but also the pre-resonant one.