Objective To investigate the effect of high-fat diet on expression of cell adhesion molecules (VCAM-1, ICAM-1) during thoracic aortic aneurysm formation. Methods Thirty adult male Wistar rats were randomly divided into three groups: sham group, surgery group and high fat group. The thoracic aortic aneurysm model was induced by CaClSUB>2/SUB>. The thoracic aortic segments were collected 4 weeks after surgery. Orcein staining and HE staining were used to observe the morphological changes in thoracic aorta. Immunohistochemistry was performed to detect the expression of CD45、VCAM-1 and ICAM-1 Results Compared with surgery group, the high fat diet group had more obvious dilation of arterial diameter, more extensive damage to the arterial wall which was associated with more serious inflammatory cell infiltration and the increased expression of VCAM-1, and ICAM-1. Conclusion High-fat diet promotes the VCAM-1 and ICAM-1 expression in thoracic aortic aneurysm wall, which may play an important role in the formation of thoracic