Asthma is a disease characterized by chronic inflammation of the airways and airway hyperresponsiveness. Clinical manifestations are recurrent episodes of expiratory dyspnea with croup, chest tightness and cough, which are mostly reversible and may resolve on their own or with treatment. The diagnosis of asthma is mainly based on medical history, symptoms, signs and necessary laboratory tests, especially pulmonary function tests. 1.Recurrent attacks of wheezing, shortness of breath, chest tightness or cough are mostly associated with exposure to allergens, cold air, physical or chemical irritation, viral upper respiratory tract infection, exercise, etc. 2.Dispersive or diffuse, expiratory phase dominated croup can be heard in both lungs during the attack, with prolonged expiratory phase. 3.The above symptoms may be relieved by treatment or may resolve on their own. 4.Except wheezing, shortness of breath, chest tightness and cough caused by other diseases. 5.In case of atypical clinical manifestations (such as no obvious wheezing or signs), at least one of the following tests should be positive: ① positive bronchial excitation test or exercise test; ② positive bronchial diastolic test; ③ intra-day variation rate or diurnal fluctuation rate of peak expiratory flow ≥ 20%. Those who meet 1 to 4 or 4 or 5 can be diagnosed as asthma. Once the diagnosis of asthma is clear, the severity of the disease can be graded according to the patient’s clinical manifestations, lung function indices, and response to the chosen treatment regimen. This classification can be divided into three parts: asthma severity classification before treatment, asthma severity classification during treatment, and asthma severity classification during an acute asthma attack, the purpose of the classification is to adopt a standardized stepwise classification of asthma treatment. The causes of asthma are very complex, with intrinsic genetic factors and extrinsic environmental factors. There are many triggers for an acute asthma attack, the common ones being dust mites, pollen, fungi, animal allergens, insect allergens, respiratory infections, irritating or noxious gases, occupational chemicals, food, medications, climate, exercise and psychiatric factors. Long-term asthma attacks can lead to airway smooth muscle hyperplasia and airway narrowing, resulting in irreversible airway obstruction. Airway inflammation persists in asthma patients whether in acute exacerbation or remission, so asthma requires long-term treatment and management. However, this chronic airway inflammation differs markedly from bacterial inflammation and therefore does not require long-term antibiotic therapy, but rather long-term treatment with medications such as inhaled glucocorticoids. Common complications of asthma include emphysema and pulmonary heart disease, pneumothorax and mediastinal emphysema, pulmonary atelectasis, respiratory failure, cardiac arrhythmias, shock and sudden death, which must be detected and managed promptly.