On the question of why we humans are nearsighted, there are a variety of online presentations, many reasons, but there are a few reasons are more recognized. Today, I have compiled a list of these causes of our myopia: First, genetic factors. This is a point of view shared by many scholars and experts, but this does not mean that myopia will be 100% inherited to the next generation, but that in many cases of myopia in children are found to have genetic factors in it, especially the heredity of high myopia is more obvious. Most research data conclude that autosomal recessive inheritance is present, so that the father and offspring may not be myopic at the same time. Second, environmental factors. This is the oldest theory, although there is still some controversy, but from a large number of domestic and foreign research reports, it has been recognized that genetics and environment are the main causes of myopia formation, and pointed out that environmental conditions are objective factors that determine the formation of myopia. Furthermore, physical factors. Some experts believe that some myopic patients’ myopia formation has some relationship with their own physical and nutritional deficiencies, and they analyzed from some data that the lack of trace elements such as cadmium, strontium and zinc and the weakness of the body can affect the occurrence of myopia, but there is no clear statement on the way through which these factors affect myopia. Currently, there are no written rules or definitions of the causes of myopia in medicine, except that the causes of myopia are complex and can be triggered by a variety of factors, both congenital and acquired, and may be the result of a combination of factors.