Acute asthma exacerbations are an important public health problem and a major cause of disease progression and healthcare burden for people with asthma. Frequent acute exacerbations are likely to be a distinct asthma phenotype. Further research is needed to identify risk factors for frequent acute exacerbations, but previous studies have mostly been cross-sectional studies at a single time point or prospective studies based on smaller sample sizes. Moreover, most of the studies on frequent acute exacerbations have been conducted in severe or refractory asthma, whereas a certain proportion of non-severe asthmatics may also experience frequent acute exacerbations, the risk factors of which remain to be further evaluated. The main objectives of this project are to compare the baseline clinical, inflammatory, pathophysiological, comorbidities, environmental pollutants and meteorological exposure characteristics of patients with frequent acute exacerbations and those with non-frequent acute exacerbations irrespective of asthma severity, and to develop a disease prediction model for frequent acute exacerbations; and to develop a cohort of patients with frequent acute exacerbations of asthma, observe their prognosis and response to treatment, and search for prognostic factors associated with them. The successful implementation of this study will help in the early identification of patients with frequent acute exacerbations, clarify the factors associated with poor prognosis in this group of patients, and thus provide an individualized plan for the treatment and prevention of this type of patients, which is of great significance in achieving good asthma control, reducing the burden of disease, decreasing the cost of healthcare, and saving clinical healthcare resources and costs.