With the expansion of the scale of "DC power grid" and the increase of transmission distance, overhead line has become the best choice to construct DC transmission network. Compared with cable lines, overhead lines have higher failure rate and are more prone to break down. Based on the topology of multi-terminal flexible DC loop network, the transient characteristics of converter stations and connected lines after disconnection fault are studied in this paper. The mechanism of DC side overvoltage and non-fault line overcurrent after fault is described. In order to suppress the transient components and speed up the system recovery, an improved current controller model is proposed. Finally, a four-terminal loop network model based on PSCAD/EMTDC is built to verify the effectiveness of the proposed control strategy, which can significantly suppress the peak overcurrent and improve the transient characteristics of converter station during fault.