The cause of asthma is mainly affected by environmental factors, as well as the asthma patient’s own factors. Asthma patient’s own factors: First, genetic, asthma and polygenic inheritance related, with obvious family aggregation tendency. Second, atopic, asthma patients themselves airway eosinophils high. Third, airway hyperresponsiveness, that is, the normal does not cause or mild stimulation will appear excessive airway constriction response, airway inflammation is the most important cause of airway hyperresponsiveness. Fourth, obesity, overweight, less activity. Fifth, environmental factors are mainly dust mites, fungi, pollen, etc. can trigger asthma. Sixth, then there is occupational sensitization, there are some flour, animal fur is also easy to cause asthma. Seven, there are drugs, food and additives, easy to trigger asthma drugs such as propranolol, aspirin, etc., food is milk, eggs, seafood and so on. Eight, then there are infections, respiratory infections and asthma have a certain relationship, the most common is the rhinovirus, bacteria and so on. Nine, there is tobacco exposure is smoking, air pollution these factors are closely related to the onset of asthma.