Objective To analyze the distribution characteristics of blood flow and wall shear stress with the consideration of elasticity of the artery wall and to investigate the biomechanical factors inducing aneurismal rupture. Methods The three-dimensional patient-specific internal carotid artery aneurysm model was constructed based on two-dimensional medical scan images. The artery wall model was created based on the statistical data of human body. According to the condition of the pulsatile blood flow in human body, hemodynamics in internal carotid aneurysm with fluid structure interaction was simulated using finite volume method and finite element method. Results An obvious vortex flow in aneurismal cavity was found with the direction unchanged during a cardiac cycle. There was a region at the aneurismal neck and aneurismal dome where the value of wall shear stress was relatively high. It also found two regions in the aneurismal neck and the aneurismal dome where the value of Von Mises Stress reached the maximum locally. In view of the material strength, it should be easy to have aneurismal rupture in these areas. Conclusions The distribution characteristics of vascular wall stress can be obtained by the calculation of fluid structure interaction to further predict the possible position of aneurismal rupture.