Objective To investigate the pathological changes of ultrastructure of mucosa in various bronchial segments from type 2 diabetic patients. Methods Sixteen cases of type 2 diabetic patients were selected, 23 pieces of bronchial mucosa and submucosal tissue of the lesion were taken from various bronchi during bronchoscopy and these samples were observed under a transmission electron microscope. Results The basal lamina of bronchial capillary were diffusely thickened and mostly showed onionskin like change, protein deposited around and BR> mixed with basal menbrance; irregular highly electron dense materials were found to deposite around capillary, capillary lumen became narrow or even collapsed,neutrophilic leucocyte marginated in lumen and adhered with endothelium; protein deposited in the interstitial; endothelial cells and pericytes had dark cell changes.The cistern of rough endoplasmic reticulum dilated and vesicle formed. Conclusion Bronchial mucosa and its surrounding tissues show characteristic pathological changes of diabetes, bronchial is also the target organ of chronic diabetic damage. BR>