Bronchopulmonary dysplasia (BPD), also referred to as chronic lung disease (CLD) of prematurity, is the most common chronic lung disease of infants and childhood,which was first reported and defined by Northway et al. in 1967. It frequently occurs in preterm infants. This current article presents information on domestic and international incidences of BPD,clinical characteristics of “old” BPD and “new” BPD,development of definition for BPD and its diagnosis criteria.