Objective: to study the pulmonary diffuse ground glass shadow application value of CT diagnosis and differential diagnosis.Methods: selected from December 2010 - DGGO in December 2012, 120 cases of patients, the clinical data of patients were retrospectively analyzed.Results: the patients with alveolar proteinosis disease and patients with viral pneumonia, both show the chamber appeared abnormal situation.Conclusion: this kind of disease of morphology, distribution and the dynamic change were analyzed, and effective for patients with narrow examination.