Objective The aim of this study was to investigate the effect of lysyloxidase inhibitor betaaminopropionitrile(BAPN) on the aortic wall in rats, to analyze the gross and pathological changes of arterial and othertissues of rats treated with BAPN at different concentrations, and to compare with the characteristics of human dissected aneurysm. Methods Eighteen SPF SD rats (4-5-week old) were divided into three groups: SD-0. 2 (Group A), SD-0. 4(Group B), and SD-0. 6 (Group C). The groups A, B and C were given 0. 2%, 0. 4%, and 0. 6% BAPN solution,respectively, as drinking water for seven weeks. Forty SPF C57BL/6 mice (3-week old) were randomly divided into four groups: C57-0. 2 (Group D), C57-0. 4 (Group E), C57-0. 6 (Group F) and the control group and given 0. 2%, 0. 4%,or 0. 6% BAPN or distilled water as drinking water, respectively, for seven weeks. All experimental animals were free to drink water. The daily water intake was recorded and the weight was measured once a week. Rats that died during theexperiment or survived after the experiment were dissected. The aortas were dissected and visually examined. The aorta was divided into four parts: ascending aorta, descending aorta, abdominal aorta above the renal artery and abdominal aorta under the renal artery. The aortic tissues were cut into 4 μm sections and stained with hematoxylin and eosin for pathological examination. The vascular diameter, and area of the tunica media were measured by image analysis. The pathological changes of aorta and dissecting aneurysm of 10 patients were also observed and compared with the rat aorta with dissecting aneurysms. Results BAPN significantly affected the water intake and weight gain of rats or mice. BAPN caused thickening of the tunica media in the aorta of rats or mice, and reduction and disordered arrangement of elastic protein. Their pathological changes were similar to the pathological changes of human aneurysms. Conclusions The incidence of dissecting aneurysm in C57BL/6 mice was much higher than that of SD rats, indicating that mice may be an ideal animal model for further study. In SD rats, the rate of pathological changes in other systems, such as intestinal rupture and scoliosis, was higher than that in the dissection aneurysm. Further exploration for SD rats as an animal model of aortic dissecting aneurysm is needed.