Asthma may evolve into chronic obstructive pulmonary disease (COPD), or develop to symptoms and signs of incompletely reversible airway obstruction accompanied by increased and reversible airway obstruction. This is called as asthma-COPD overlap (ACO). In this article we reviewed the advanced researches on the diseases, and made a summary in the aspects of the definition, diagnostic criteria, incidence rate and the related factors, clinical phenotype and pathogenesis, clinical features, prognosis and treatment, in order to have a better awareness of this new type of disease and provide help for clinical diagnosis and treatment.