A height of 140cm for an eleven year old boy is usually normal. The normal range of height for an 11-year-old boy is 125.7-165.8cm, and the median is 145.3cm, so the height of an 11-year-old boy of 140cm is in the normal range and is normal. Children’s height is very much influenced by the genetic factors of their parents’ height. Ensuring a healthy lifestyle, early to bed and early to rise, adequate dairy products and a balanced diet, and proper exercise will help children’s height development. Genetic factors cannot be intervened, therefore, parents can mainly promote height development by ensuring that their children have a reasonable diet structure, adequate sleep and outdoor activities. It is important to note that children’s height growth is not an equal rate of increase, and should be evaluated on the basis of the individual child’s own changes, rather than taking the so-called “normal value” as a “standard” for evaluation. If there is any abnormality, it is recommended to consult a doctor in time.