【Abstract】 Objective To investigate the diagnostic value and image quality analysis of low dose multilayer spiral CT in the diagnosis of children with bronchial foreign body.Methods 72 children with bronchial foreign bodies diagnosed by fiberbronchoscopein respiratory department of our hospital from February 2015 to December 2017 were selected and divided into three groups according to the random table method, each with 24 cases, namely low tube voltage group (80kv), middle tube voltage group (100kv) and high tube voltage group (120kv). All the CT data were postprocessed by techniques including multiple plane reformation (MPR),curved planar reconstruction (CPR), minimum intensity projection (MinIP),then compared with bronchoscopy. Meanwhile, the image quality of different tube voltages was analyzed.Results A 72 patients underwent multislice spiral CT scan with no grade III images, and no statistic difference was found in the image quality among three groups (P＞0.05). Xray radiation dose received in scanning among three groups ranked in an ascending order was low tube voltage group, middle tube voltage group and high tube voltage group, with statistic difference (P＜0.05). Coincidence rate of foreign body localization was 91.7% (65 cases) compared with bronchoscopy, with 83% (6 cases) foreign body position not consistent. The difference between the bronchoscopy and multislice spiral CT was not statistic (P＞0.05). Direct signs included 38 cases (528%) of highdensity shadows such as columnar, circular, curved and irregularities in the trachea and bronchus, 28 cases (38.9%) with airway stenosis and "cutoff sign". Indirect signs included 33 cases of emphysema, 27 cases of pneumonia, 13 cases of atelectasis, 3 cases of pleural effusion, 2 cases of bronchiectasis, 3 cases of mediastinal and subcutaneous gas, 4 cases of interstitial emphysema, 30 cases of mediastinal shift.Conclusion The application of the low dose multilayer spiral CT can accurately display the size, position and shape of foreign bodies of children with bronchial foreign body, which can reduce the Xray radiation dose received in scanning, without impact on the image qualities, so it is worthy of promotion.