The main goal of this study is to investigate the role of vascular graft thickness in wall stress gradient in anastomosis region. Atherosclerosis is a common heart disease causes high mortality rates every year. The gold standard treatment of atherosclerosis is replacing with autologous vein extracted from patient's body. Since proper autologous vein is limited, researchers have made efforts to achieve compliance engineered blood vessels. Mechanical stress has great effect on both smooth muscle cells and endothelial cells and it is considered as a stimulus in plaque formation. In this study, we evaluate the role of thickness in wall stress of anastomosis region. For this purpose, two anastomosis models have been provided in ADINA and FSI simulations have been performed during pulsatile flow. In addition, the sensitivity of compliancy to thickness and diameter has been investigated. The vascular graft used in the simulations is a synthetic graft made up PCL and PVA by our group. Results show that thickness is an important parameter and even if vascular graft is compliant, improper thickness leads to an increase of wall stress pressure in anastomosis region.