A knowledge graph construction system and method are disclosed. The system generates a recommended subject entity, at least one recommended object entity, and at least one recommended relation for a piece of text data according to the text data and a plurality of triples. The system displays the recommended object entity and the recommended relation at a current paragraph of the text data according to the recommended subject entity for user to select. The system receives a confirmed message related to the recommended subject entity, a recommended object entity selected by user from the at least one recommended object entity, and a recommended relation selected by user from the at least one recommended relation. The system adds the recommended subject entity and the selected recommended object entity and recommended relation to the triples, and constructs a current knowledge graph by using the triples according to the confirmed message.