As an important resource for emerging industries, critical metals have gradually gain attention both domestically and overseas in recent years. However there are still some bottlenecks existing in the critical metal research due to its low abundance, difficulty to trace, identify and separate. As an important infrastructure of big data and artificial intelligence, knowledge graph provides new insights to tackle these issues. Most of the research achievements related to critical metal deposits are published in academic journals, which are written in natural language and is difficult to be understood and directly used by machines. In this paper, the ontology layer of Nb-Ta deposit knowledge graph was constructed and data extracted from literatures consists of the fact layer of the Nb-Ta deposit knowledge graph. Based on the Nb-Ta deposit knowledge graph, the features and relationships among the metallogenic periods, types of Nb-Ta deposits and the co-occurrence of niobium and tantalum related minerals were analyzed. It will help to further reveal the spatio-temporal distribution and evolution characteristics of China Nb-Ta deposits.