EQL, also named as Extremely Simple Query Language, can be widely used in the field of knowledge graph, precise search, strong artificial intelligence, database, smart speaker ,patent search and other fields. EQL adopt the principle of minimalism in design and pursues simplicity and easy to learn so that everyone can master it quickly. EQL language and lambda calculus are interconvertible, that reveals the mathematical nature of EQL language, and lays a solid foundation for rigor and logical integrity of EQL language. The EQL language and a comprehensive knowledge graph system with the worlds commonsense can together form the foundation of strong AI in the future, and make up for the current lack of understanding of worlds commonsense by current AI system. EQL language can be used not only by humans, but also as a basic language for data query and data exchange between robots.