Abstract: Objective：To evaluate chest HRCT ( highresolution computed tomography ) characteristics and dynamic changes in patients with novel H1N1 influenza A infection, and briefly analyzes the relationship between the imaging characteristics and clinical prognosis. Methods：Clinical data and imaging findings of 66 cases with confirmed severe and critical H1N1 were analyzed retrospectively. All of the cases received chest HRCT scans in admission to hospital and discharge, scanning interval 216 d, average followup (2.67±1.05) times. Results：Among the 66 patients, 50 cases of male and 16 cases of female, with an average age of (40.42±15.54) years old. The characteristics of chest HRCT findings and dynamic changes were as follows: patchy exudation focus of lung parenchyma was the main finding, while ground glass opacities in 3 cases. The moderate manifestation was pure consolidation focal distribution, or scattered pieces of consolidation and ground glass opacity in 24 cases, which located in the subpleural regions. The severe 35 cases manifestated with a large patch of consolidation and there was air bronchogram in the consolidation. Examination in over 3 days showed the progress in pathological changes. Over 7 days after infection, all of lung appear multiple spot piece of shadow; consolidation and ground glass opacity in 19 cases. A large area of consolidation mainly in 10 cases, 16 cases of pleural effusion. Three days after admission, the lesions of 6 cases were obvious deterioration, 15 cases were significantly reduced, the lesions of lung can be appeared fibrosis between 41 cases. It was common that with pleural reaction, but lymph node involvement was infrequent. Conclusions：There are some radiographic characteristics in novel H1N1 influenza A infection. Severe and critical patients is easily attacked by pulmonary infection, chest disease progression, some people can lead to respiratory failure. Chest imaging examination can play an important role in the early diagnosis. Getting familiar with chest HRCT appearances and dynamic changes is helpful for its early diagnosis and the abnormal changes after medical treatment.