In the distribution power system with its neutral point grounded by an arc suppression coil connected with the damping resistance in series, the existing method for the grounded parameter measurement is not accurate enough. Therefore, an improved resonance measurement method of grounded parameters is proposed for distribution power systems. In this paper, the influence from the damping resistance on the arcsuppression coil compensation is analyzed. And then, the equivalent circuit of resonance measurement is constructed respectively for two grounding modes whose arc suppression coils connect a damping resistance in series and parallel. In addition, the mathematical expressions of the distribution power system's grounded capacitance and grounded leakage conductance are derived respectively. A current signal with characteristic frequency is directly injected into the distribution network through the neutral point connected to the constant current signal source with the variable frequency, and the characteristic voltage signal is measured through the triangular side of zerosequence voltage transformer. In terms of the grounded parameter expressions, the fast and accurate grounded parameter measurement in distribution power system is realized by exploring the system resonance frequency. The correctness of proposed method is verified by PSCAD/EMTDC simulation. It is shown that this method has the high precision and wide application.