Abstract: Hybrid AC/DC distribution network is an effective solution for the transition from AC distribution network to DC distribution network. To improve the transmission capacity and power supply reliability of hybrid AC/DC distribution network, the multi-terminal power supply structure is widely used. Starting with the two-terminal power supply structure, the DC-side fault characteristics and grounding mode are studied when the single-pole grounding fault occurs. Through the analysis of the fault circuit, the stage performance of the current after fault is studied. The time expression of the fault voltage and current is obtained,and the simpler calculation formula of the peak value and the peak time of the fault over-current is deducted through mathematical simplification. On this basis, the method for selecting the grounding resistance value is given by an example. When the parameters of both sides of the circuit are asymmetric, the phenomenon and law of the fault current oscillation are studied and analyzed, and a circuit calculation method of the four-order differential equation based on the equivalent splitting method is proposed to calculate the fault current. The simulation results show that the proposed calculation method and grounding mode are suitable for the DC side of the two-terminal hybrid AC/DC distribution network, and contribute to the safe, stable and reliable operation of the hybrid AC/DC distribution network.