Objective To explore the influencing factors for the severity of bronchopulmonary dysplasia (BPD) in preterm infants. Methods The clinical data of 110 preterm infants who were diagnosed with BPD and had a hospital stay of over 28 days between January 2011 and December 2013 were analyzed. These BPD infants were divided into 3 groups according to the clinical criteria: mild group (n=52), moderate group (n=44), and severe group (n=14). The relationship between the severity of BPD and the gestational age, birth weight, asphyxia, oxygen therapy, pregnancy complications, intrauterine pneumonia and mechanical ventilation was analyzed. Results The severity of BPD was correlated with the following factors: gestational age, birth weight, prenatal infection, duration of oxygen inhalation with a concentration of >40%, use of mechanical ventilation, parameters and duration of mechanical ventilation, duration of continuous positive airway pressure, adoption of intubation surfactant extubation (INSURE) approach, Ureaplasma urealyticum infection, intrauterine pneumonia and patent ductus arteriosus. Logistic regression analysis indicated that the mechanical ventilator parameter peak inspiratory pressure (OR=1.260, 95%CI: 1.096-1.448) and duration of mechanical ventilation (OR=1.010, 95%CI: 1.005-1.016) were independent risk factors for the severity of BPD, while the INSURE approach was a protective factor (OR=0.208, 95%CI: 0.060-0.923). Conclusions The severity of BPD is associated with various factors in preterm infants. The important measures for preventing BPD include avoiding the birth of preterm infants with a very low birth weight, shortening the duration of mechanical ventilation, preventing and reducing pulmonary infections, and applying the INSURE approach.