Objective To investigate the expressions and significance of transforming growth factor-beta 1(TGFβ1) and its typeⅡ receptor (TGFβRⅡ) in experimental rat ascending aortic aneurysm of rat model. Methods The rat ascending aortic aneurysm models were made by banding ascending aorta of young Wistar rats. The ascending aortas were taken 4 months after operation. Immunohistochemistry staining and Western blotting were used to investigate the expressions of TGFβ1 and TGFβRⅡ.Result Immunohistochemistry staining results showed that TGFβ1 expressed in all layers of the aortic aneurysm and the control. TGFβRⅡ was extensively located in the hyperplastic intima and tunica media smooth muscle cells in the aortic aneurysm, while there was only a little positive staining in the control group. Western blotting results indicated that the expression levels of TGFβ1 and TGFβRⅡ in the aortic aneurysm were stronger than the co