Spread of atherosclosis illness in aorta causes many problems in blood circulating. Hemodynamic factors perform an important role in this illness. Hence making an effective coupling between fluid and structure in continuous/pulse modes is the main challenge. In recent years, the lattice Boltzmann Method (LBM) which is obtained from kinetic theory has been advanced numeritically. It is a simple numerical method which has some advantages such as easy implementation, highly desirable for parallel computing and second order accuracy. It is a proper and efficient method for solving fluid flows at low Mach numbers. The purpose of this project is to simulate pulsatile blood flow in flexible vessels. From the theoretical point of view, Fluid Structure Interaction problems is extremely difficult because of the high non-linearity of the governing equations and the low regularity of the displacement of the fluid–structure interface. The fluid equations are solved by lattice Boltzmann method and the structure equations are solved by dynamic finite element method (by Fortran programming). We used explicit 2-way coupled method for coupling of the fluid-wall interactions and then applied the force created by fluid to the solid structure domain. Then displacements and velocities at the wall are calculated from the solid part and used for the fluid. We used two separate solvers for solid and fluid parts. Solid has been considered as axisymmetric and linear elastic substance with fixed constraint at inlet and outlet. Proportional damping is applied for simulation of solid damping. The implicit Newmark method is used for time integration. The fluid model that used in lattice Boltzmann method is a two-dimentional and Newtonian model. In this study laminar flow was assumed. In this project, the effect of elasticity of vessel wall on velocity profile and shear stress has been evaluated in different inlet and outlet boundary conditions. The inlet velocity and outlet pressure boundary conditions are used in the simulations. At first stage, the differences between flexible and rigid states have been considered at constraint of constant inlet velocity and outlet pressure. Then the effect of pulse inlet velocity has been studied. The effect of various damping of vessel wall on results has been considered. The results show the ability and strength of LBM for simulation of fluid structure interaction. We compared the velocity profiles of two different states, first when we consider positive acceleration at inlet and constant pressure at outlet, second negative acceleration at inlet and constant pressure at outlet. The comparison showed that velocity profile becomes smoother at the first state than later. The simulations show that the velocity profile is more uniform for the flexible state and so the shear stress in this state reduces. Finally, pulsative inlet pressure and constant outlet pressure have been considered where damping affects results more than it did in the previous case. Moreover, the less the damping is, the flatter the velocity profile becomes. Keywords: Lattice Boltzmann Method, blood, Finite Element, Fluid-Structure Interaction