Objective To classify the segmental bronchial patterns of the left upper lobe by combining three post-processing images from 64 slice spiral CT and to study how to identify different ramifications in transverse thin-section CT. Methods Totally 204 patients with routine thorax scans were enrolled. The segmental bronchi were demonstrated in terms of bronchial tree, virtual bronchoscopy and thin-section CT three post-processing images. Integrated with the three post-processing images, the segmental bronchial patterns of the left upper lobar bronchi were classified into several main types, and displayed in transverse thin-section CT. Results The segmental bronchial ramifications of the left upper lobe were classified into three types mainly: common stem of apical and posterior segmental bronchi (64%, 130/200), trifurcation (23%，45/200), common stem of apical and anterior segmental bronchi (10%, 21/200), and they could be identified in two typical slices of transverse thin-section CT. There were two dominating types in the left basilar segmental bronchi: bifurcation (75%, 163/216), trifurcation(18%, 39/216), and they could also be identified in two typical slices of transverse thin-section CT. Conclusion The segmental bronchi of the left lung can be definitely classified by three post-processing images from 64 slice spiral CT.