Abstract： Objective To describe the characteristics of and emergency treatment for and outcomes of critical ill children with 2009 influenza A caused by H1N1 virus strain. Method A prospective observational study of 3 pediatric patients with severe influenza A of H1N1 virus strain complicated with acute respiratory distress syndrome (ARDS) from November to December 2009. Results The H1N1 virus strain was confirmed by using realtime reverse transcription polymerase chain reaction (Real-time RT-PCR). Two patients survived and one died. Fever and cough were the onset symptoms. The systemic responses to influenza A at first were relatively mild. The tragic deterioration occurred all of a sudden with cyanosis all over the lips and dyspnea. The roentgenography showed bilateral multiple tabular pulmonary effusion and diffuse opaque shadows. The length of time required to confirm the diagnosis of ARDS from the symptom onset was 4 to 6 days. All patients were severely hypoxic with the ratio of PaO2 to 0.7-0.9 fraction of inspired oxygen (FiO2) to be 70- 100 mmHg at admission to PICU. In order to avoid injury to the lung, the protective ventilation strategy was carried out with low tidal volume (6 mL/kg) and adequate pressure,and conservative fluid management. Conclusions The H1N1 strain influenza virus A is characterized by pyrexia, cough and other respiratory symptoms in the early stage of critically ill children. In a few days, cough increased along with a sudden burst of cyanotic lips and shortness of breath, highly suggesting ARDS. Timely oxygen therapy and respiratory support, conservative fluid management, and the prophylaxis of secondary infection may be the essential measures. More clinical data are needed to clarify the critical features and to evaluate the emergency therapy for H1N1 influenza A in critically ill children.