ADHD, also known as attention deficit hyperactivity disorder (ADHD), is one of the most common psychiatric behavioral disorders of childhood, with a prevalence of about 6%-9% in school-age children. There are significant differences compared to normal children. It is now believed that ADHD is a syndrome closely related to neurodevelopment caused by multiple biological, psychological, and social factors acting alone or in concert. The causes of ADHD are summarized as follows: 1. Genetic factors: Familial and dizygotic studies have shown that genetic factors are an important cause of ADHD. Molecular genetic studies have shown that ADHD is a polygenic genetic disorder closely related to neurodevelopment. Organic brain factors: Studies have found that maternal infection during pregnancy, exposure to toxic substances, malnutrition, smoking, alcohol consumption, intrauterine distress due to various causes, abnormal delivery, low birth weight babies, and central nervous system infection or traumatic brain injury within 1-2 years after birth may lead to abnormal neurodevelopment in children and increase the risk of ADHD. 3, central neurotransmitter abnormalities: neurobiochemical studies found that children with ADHD have insufficient norepinephrine function, insufficient dopamine function, and excessive or relatively insufficient 5-hydroxytryptamine function in the brain, and these neurotransmitters are thought to activate the cerebral cortex or reinforce social behavior, thus presumably the cause of ADHD may be a behavioral disorder caused by neurotransmitter dysregulation. 4, psychosocial factors: poor family environment and social environment are likely to increase the risk of ADHD in children. Children living in a disharmonious family environment are often in a state of tension, depression, fear, anxiety and conflict, and are prone to behavioral problems such as impulsivity and hyperactivity, inattention and emotional instability, or aggravate certain symptoms of ADHD. Inappropriate education is also one of the risk factors for ADHD. Simple and violent education methods, over-indulgence or over-protection can all be triggering factors for ADHD. 5. Other factors: Some studies have found that excessive consumption of lead-containing foods by children and high blood lead levels in the body may be related to hyperactivity and inattention, which may be a potential cause of ADHD. The exploration of the causes of ADHD has practical guidance for choosing the right treatment method, and the comprehensive treatment measures such as medication, psychotherapy and adjustment of educational environment (family and school) can better improve the prognosis of the affected children and make them grow up healthily according to their specific conditions.