How to extract useful information from surging data has become a critical issue confronting artificial intelligence in the Internet age. As an important method, knowledge graph has become the main driving force to promote the development of artificial intelligence technology. Information extraction realizes the extraction of structured entities and their relationships from massive data, which is the primary step in constructing a knowledge graph. This study discusses the development trend of information extraction in knowledge graphs, as well as entity extraction, relationship extraction, event extraction, and key technologies. Finally, it analyzes and discusses the current problems, challenges, and future development.