Nail biting is a common bad habit in childhood. Most nail biting behavior can disappear on its own as we get older, but a few stubborn people can continue into adulthood. The main reasons for nail biting are: 1. mental reasons. When adults are in a stressful and anxious situation, feeling the pressure of life will subconsciously bite nails, in order to relieve emotions and relax the pressure; when children are enrolled in school or when they are sick, they are prone to emotional tension, depression, frustration, these negative emotions may also be caused by parents’ lack of attention or insecurity, which can also trigger this behavior. 2. Lack of trace elements. When the body lacks trace elements such as zinc, iron and calcium, children may be triggered to bite their nails. 3. Imitation of peers. Some children do not have the habit of biting their nails, but when they see their friends around them biting their nails, they usually like to imitate their peers, and in this case, the child will unconsciously develop the habit of biting their nails. Children who are more introverted and sensitive are more likely to suffer from this disease. Therefore, I hope that parents can correctly understand the causes of nail biting, treat their children rationally and help them to change this bad habit.