Abstract: Power secondary equipment is a barrier to ensure the safety and stability of power system. It can improve the information utilization rate of each stage of its life cycle and evaluate the quality of equipment more comprehensively. In this paper, all kinds of data in the whole life cycle of secondary equipment are preprocessed. Through the analysis of the characteristics of domain terms, the labeling specifications and rules are formulated, the domain professional corpus is established, and the domain ontology of the whole life cycle of power secondary equipment is constructed. Using the graph database to realize the storage of domain knowledge graph, complete the construction of domain knowledge graph, realize the knowledge query of nodes and relationships, integrate the fragmented information of the whole life cycle of power secondary equipment, and break the information island of each stage.