The transition from passive power distribution network to active power distribution leads to the change of network structure, which results in the significant increase of risk in operation and maintenance work. This paper proposes a verification method about the safety of grounding wire in medium-voltage active distribution network based on Ondendonks formula. Considering the situation that the staff in the medium voltage side for maintenance, the distributed generators are divided into two types, which are rotating machine-based generator and inverter-based generator. On this basis, the short-circuit current generated at the grounding device due to mis-operation and device reasons is calculated according to the superposition theorem. The cross-sectional area of the grounding device is selected by using the Ondendonks formula preliminarily, and then the secondary check is carried out by calculating the single-phase and three-phase residual voltage. Finally, reliable grounding measures can be obtained on the basis of the actual topology. The feasibility and effectiveness of this method are validated by the application in a practical case.