Objective Although CT and bedside X-ray are available to diagnose pneumonia, there is still an urgent need for a convenient, effective bedside examination to accurately diagnose pneumonia especially in critically ill patients. The purpose of this study was to explore the application of bedside pulmonary ultrasound in the anatomical location and size determination of pneumonia. Methods Familiarizing pulmonary anatomical localization of healthy people with pulmonary ultrasonography, 40 patients with community acquired pneumonia who were hospitalized in the Affiliated Hospital of Nantong University from January 2015 to January 2019 met the diagnostic criteria of community acquired pneumonia were examined by bedside ultrasonography and chest CT scan at the time of admission. The anatomical location of pulmonary inflammatory lesions was localized and the size of the infected lesions was quantitatively compared. Results Bedside ultrasound can clearly display pulmonary anatomical localization and accurately determine the size of pulmonary infected lesions. Conclusion Bedside pulmonary ultrasonography has clinical application value in the anatomical location and size judgement of pulmonary infection focus.