The study investigates the interaction between vertebral artery stenosis and pulsatile blood flow, with a focus on the mechanical properties and internal dynamics of blood flow. First, an asymmetrical stenosis mathematical model was established to reveal the relationship between the resistance ratio and shear stress ratio and their dependence on stenosis height and length. Next, various stenosis models were constructed using medical imaging data and analyzed through computational fluid dynamics (CFD) and fluid-structure interaction (FSI) methods. Finally, hemodynamic parameters, such as blood flow velocity and time-averaged wall shear stress (TAWSS), along with solid mechanics indicators, including total deformation and von Mises stress, were evaluated. The results indicate that changes in stenosis length and height significantly affect the resistance ratio and shear stress. Whole-segment stenosis in the vertebral artery may lead to thrombosis and intimal damage. In contrast, stenosis at the ostium of the vertebral artery increases the risk of platelet deposition on the vessel wall, potentially triggering atherosclerosis. This could ultimately lead to insufficient blood flow to the brain due to impaired vertebral artery circulation. FSI simulations revealed that elastic vessel walls are more sensitive to high-velocity flows, especially in stenotic and downstream regions. These findings provide critical insights into the effects of stenosis on blood flow and are crucial for developing effective clinical intervention strategies.