Explanatory writing is an article genre with explanation as its main expression. Through the scientific explanation of physical things, objective things or abstract things, it makes people have a scientific understanding of the shape, structure, nature, types, causes, functions, relationships or concepts, characteristics, sources, evolution, similarities and differences of things. So as to acquire relevant knowledge. Explain that the text center is distinct and prominent, the article is scientific and organized, and the language is accurate and vivid.