Bronchial asthma is one of common diseases of respiratory system, but its causes and pathogenesis can not be explained clearly. Among various pathogenic factors and predisposing factors, including respiratory viruses, bacteria, mycoplasmas, fungi, etc, respiratory infection plays an important role in the incidence of asthma. This paper reviews the correlation among airway bacterial colonization, pathogenesis of asthma, and refractory asthma.