Aim To investigate the clinical applicative value of multislice spiral CT angiography (MSCTA) in the diagnosis of aortic dissections (AD). Methods MSCTA was performed on 21 patients with AD. The computed tomography was carried out with scanning thickness of 2.5 mm, reestablishing interval of 1.6 mm, pitch of 1.25, control reagent of 100 mL in an infusing speed of 3 mL/s, and a delay time of 18～20 s. All data were imported into the workstation and analyzed by maximum intensity projection (MIP), multiplanner reformation (MPR), shadow surface display (SSD) and volume rendering (VR). Results Among the 21 patients, there were 5 cases for Debakey type Ⅰ, 3 for type Ⅱ and 13 for type Ⅲ. All the images by MSCTA showed the whole length of aorta, real and false cavities, endothelium layer and aortic aneurysm with a very good quality. Conclusion MSCTA is of important clinical value in the diagnosis and treatment of AD.