The protection technology of medium and low voltage DC distribution system is still in its infancy, and its accuracy is not high in the process of practical application. Therefore, a fault identification method of medium and low voltage DC distribution system based on high-frequency fault component is proposed, and the topology, grounding mode, protection equipment Fault type and fault transient characteristics are closely related to the design of protection scheme. Based on the high-frequency fault component, the fault identification algorithm of medium and low-voltage DC distribution system is optimized, and different fault categories of AC and medium and low-voltage DC distribution system are divided, so as to achieve the research goal of accurate positioning of different fault types. Finally, it is confirmed by experiments. The fault identification method of medium and low voltage DC distribution system based on high frequency fault component has high accuracy and fully meets the research requirements.