Recent studies have suggested that obstructive sleep apnea hypopnea syndrome (OSAHS) is an independent risk factor for acute exacerbation of bronchial asthma. OSAHS commonly involves inhaled airflow limitation and upper airway collapse during sleep, and is usually associated with some daytime symptoms such as sleepiness, depression, poor concentration, and so on. Bronchial asthma is usually manifested as chronic inflammation, hyperresponsiveness and reversable airflow limitation of airway. So far, many researchers have investigated this association, however, no consensus has been reached. It is generally regarded that following factors are involved in the interaction mechanisms of OSAHS and asthma, that is, neural reflection, gastroesophageal reflux, airway and general inflammatory response, sleep structure disturbance, obesity, cardiovascular diseases, oral steroid use, nasal disorders, and so on. This article reviewed the association between OSAHS and asthma and its mechanisms.