Objective To evaluate the diagnostic value of lung ultrasonography for transient tachypnea of newborn (TTN). Methods From January to December 2014, a total of 1 358 children were hospitalized in the Neonatal Intensive Care Center and underwent lung ultrasonography at the Bayi Children's Hospital, Beijing Military General Hospital.According to the patients' medical histories, clinical presentations, arterial blood gas analysis, chest X-ray examinations, and lung ultrasound examinations, there were 412 cases of patients without pulmonary lesions, 228 cases of TTN, 358 cases of respiratory distress syndrome (RDS), 85 cases of meconium aspiration syndrome (MAS), 215 cases of infectious pneumonia, and 60 other cases at the time of hospital admission.In a resting state, the patients were placed in a supine, lateral recumbent or prone position.By using the anterior and posterior axillary lines as boundaries, the lung was divided into 3 regions: anterior, lateral, and posterior.The probe was perpendicular or parallel to the ribs, and each region of both sides of the lung was scanned.The scan results were compared to the conventional chest X-ray results. Results The main ultrasonic characteristics of TTN was pulmonary edema.In severe cases, the ultrasound showed a white lung or compact B-line.Compact B-line had 100.0% sensitivity and 95.3% specificity for diagnosing severe TTN.Mild TTN presented as pulmonary interstitial syndrome or double lung point.Double lung point might appear during the recovery period of mild TTN or other diseases, such as RDS, MAS, and pneumonia, among others.Lung consolidation and air bronchogram were not observed in patients with TTN.Pleural effusion might occur in a variety of lung diseases, and pleural line abnormality, A-line disappearance, and B-line or pulmonary interstitial syndrome were common ultrasonic manifestations of a variety of lung diseases. Conclusions Ultrasonic diagnosis of TTN, mainly based on pulmonary edema without lung consolidation and air bronchogram, is accuracy and reliable; however, double lung point is not a specific sign of TTN, whereas the identification of a white lung and compact B-line is a sensitive and specific sign of severe TTN. Key words: Transient tachypnea; Lung ultrasound; Infant, newborn