Compared with AC distribution network, many problems should be solved in DC distribution network, such as fault current limiting, fault current blocking and power quality control. In order to reduce the number of equipment in DC system, a multi-functional fault current controller topology based on LCL structure is proposed, which has the capacity for fault current limiting, fault current blocking and voltage regulation. On account of the topology structure, the operation principle of LCL structure under different working objectives is studied, and the multiplexing process of filtering and limiting current of LCL structure is clarified. A fast detection method of fault current is also proposed. By matching the threshold value of voltage change rate and current change rate at different positions of current limiting device, the fast judgment of bipolar fault, single pole fault and high resistance fault are realized. Finally, the system simulation model is built to verify the validity of multi-functional of the fault current controller topology, and the rapidity of fault current detection.