Aim To investigate the value of magnetic resonance imaging in the diagnosis and evaluation of aortic dissection. Methods 19 patients with aortic dissection diagnosed by using spin echo and gradient echo sequences of magnetic resonance were studied. We have discussed the diagnostic value of different sequences and positions of magnetic resonance for visualizing the intimate flap,the site of tear,origins of aortic branches and differentiating the true lumen from the false. Results Among these 19 patients with aortic dissection, 17 cases showed the intimate flap. 13 cases showed the entry tear and were classified into DeBakey typeⅠ, Ⅱ and Ⅲ in 2, 2 and 9. Conclusion Although magnetic resonance imaging has some limitations,it is the first choice for the diagnosis of aortic dissection,and is significant for the management of aortic dissection.